BEIRUT -- He is among the very last survivors of his Gaza family, a clan so close they knew without thinking how blood and marriage bound them across generations and city blocks.

Then, branch by branch, 173 of Youssef Salem's relatives were killed in Israeli airstrikes in a matter of days in December. By spring that toll had risen to 270.

Bones and flesh strewn over the ruins of family homes. Blond curls of a young cousin peeking through bricks. Unrecognizable bodies piled on a donkey cart. Lines of burial shrouds.

These images are what survivors are left with from hundreds of families in Gaza like the al-Aghas, Salems and Abu Najas.

To a degree never seen before, Israel is killing entire Palestinian families, a loss even more devastating than the physical destruction and the massive displacement. An Associated Press investigation identified at least 60 Palestinian families where at least 25 people were killed -- sometimes four generations from the same bloodline -- in bombings between October and December, the deadliest and most destructive period of the war.

Nearly a quarter of those families lost more than 50 family members in those weeks. Several families have almost no one left to document the toll, especially as documenting and sharing information became harder.

Youssef Salem's hard drive is stocked with photos of the dead. He spent months filling a spreadsheet with their vital details as news of their deaths was confirmed, to preserve a last link to the web of relationships he thought would thrive for generations more.

"My uncles were wiped out, totally. The heads of households, their wives, children, and grandchildren," Salem said from his home in Istanbul.

In the last two decades, 10 members of his family were killed in Israeli strikes. "Nothing like this war," he said.

The AP review encompassed casualty records released by Gaza's health ministry until March, online death notices, family and neighbourhood social media pages and spreadsheets, witness and survivor accounts, as well as a casualty data from Airwars, a London-based conflict monitor.

The Mughrabi family: more than 70 were killed in a single Israeli airstrike in December. The Abu Najas: over 50 were killed in October strikes, including at least two pregnant women. The large Doghmush clan lost at least 44 members in a strike on a mosque; AP documented over 100 family members killed in following weeks. By the spring, over 80 members of the Abu al-Qumssan family were killed.

"The numbers are shocking," said Hussam Abu al-Qumssan, who lives in Libya and has taken over documenting the family death toll as his relatives in Gaza struggled to keep track.

In the 51-day war of 2014, the number of families that lost three or more members was less than 150. In this one, nearly 1,900 families have suffered multiple deaths by January, including more than 300 that lost over 10 members in the first month of the war alone, according to Gaza's health ministry.

Ramy Abdu, chairman for the Geneva-based EuroMed Human Rights Monitor, which monitors the Gaza war, said dozens of his researchers in Gaza stopped documenting family deaths in March after identifying over 2,500 with at least three deaths. "We can hardly keep up with the total death toll," Abdu said.

The killing of families across generations is a key part of t he genocide case against Israel, now before the International Court of Justice. Separately, the International Criminal Court prosecutor is seeking arrest warrants for two Israeli leaders for war crimes and crimes against humanity, including for the intentional killing of civilians, as well as for three Hamas leaders over crimes connected to the Oct. 7 attack.

Palestinians will remember entire families that have disappeared from their lives, Abdu said: "It is like a whole village or hamlet has been wiped out."

Without warning

The deaths across generations slice through the Palestinian society, history, and future. Entire families are buried in mass graves, in hospital courtyards or beneath staircases in the homes where they were killed.

Getting detailed images and documentation is difficult even for Palestinians. Power is limited to hospitals and Israel cuts communication networks frequently. Nearly all of Gaza's 2.3 million population has been displaced, dividing families and severing contacts between parts of the small territory. Homes that normally would shelter a nuclear family fill with multiple generations of displaced relatives.

Hamas militants from Gaza attacked Israel on Oct. 7, killing 1,200 people in the deadliest day of the Jewish state's 75-year history. Israel promised to destroy Hamas' leadership and its estimated 35,000 fighting force in response. Within five days, Israel Air Force dropped 6,000 bombs on Gaza, including many unguided missiles.

Israel's relentless bombing since has killed more than 37,000 Palestinians by early June, including many women and children.

Eleven members of the al-Agha family were killed in a single strike on a family home in the first week of the war. Then death reached Khamis al-Agha's home in the second week.

Back in 2021, Khamis al-Agha, an employee at a Hamas-linked charity, received a phone call from an Israeli soldier alluding to his ties to the militant group and warning him to evacuate his house in Khan Younis to avoid an impending airstrike nearby. Al-Agha recorded the call and posted it online. He didn't evacuate and no one was killed.

On Oct. 14 there was no warning. The airstrike killed Khamis al-Agha and 10 others: his wife, their four young children; his brother and his 9-year-old son and 3-year-old daughter; his cousin and her 18-year-old boy. Only the brother's wife survived.

Jaser al-Agha, a second cousin of Khamis, helped medics pull bodies from the debris.

"Nothing is left of the house," said Jaser al-Agha.

Israel's army confirmed the airstrikes, saying it had hit unspecified Hamas targets near the locations identified by AP. It said the targets were anywhere from a few metres (feet) to 460 metres (1,500 feet) away. It gave no details on the nature of the targets, but said it hit a Hamas military compound in one of the strikes. It did not say whether it had taken any measures to reduce civilian casualties. In general, Israel has said it targets Hamas and accuses the militant group of endangering civilians by operating among the population and in tunnels below them.

A senior Israeli official told reporters in December that the army calculated two Palestinian civilians were killed for every Hamas militant, a ratio an army spokesman called "tremendously positive" but which experts said showed a higher tolerance for civilian casualties than in previous wars.

Israel estimates 15,000 Hamas militants had been killed by June, but has not given evidence or explanation. It is not clear whether the count includes men like al-Agha, who worked in one of the hundreds of Hamas-linked organizations or officials in the government that administered life in Gaza for over 16 years.

Israel has said it takes measures to mitigate agains t civilian harm, such as direct warnings to civilians in past conflicts. But in this war, that method has been partly replaced by evacuation orders for entire areas that not everyone is willing or able to obey. Standards have clearly been relaxed, fueled by anger over the Oct. 7 attacks and domestic politics, said Craig Jones, a lecturer at Newcastle University who studied the role of Israel's military lawyers.

The law of war allows for a "sort of rushed form of warfare" with higher civilian casualties where a military needs to respond quickly and in changing circumstances. But "Israel is just so clearly violating the law because it's pushing the rules so far," he said.

The AP geolocated and analyzed 10 strikes, among the deadliest from Oct. 7 to Dec. 24, and found they hit residential buildings and shelters with families inside. In no case was there an obvious military target or direct warning to those inside, and in one case the family said they had raised a white flag on their building in a combat zone. Together, the strikes killed more than 500 people, including the two bombings that wiped out the Salems and three others that killed 30 members of the al-Agha family. AP also consulted six weapons investigators, open-source analysts and experts.

By the spring, AP documented nearly 100 members of the al-Agha family were killed in Israeli strikes. Jaser al-Agha has buried almost more relatives than he can count, including three cousins he considered brothers.

"I was waiting for my turn," he said.

When afternoon becomes night

Ramzy Abu al-Qumssan's family lived in the Jabaliya refugee camp since his family was displaced in 1948 from Deir Sneid, a village north of Gaza in what is now Israel. Like the majority of Palestinians in Gaza, they are officially refugees, and the territory is filled with semi-permanent camps that have developed into urban communities over generations.

The Jabaliya refugee camp, in northern Gaza, was among the most densely populated. On the afternoon of Oct. 31, Abu al-Qumssan heard warplanes overheard, then a quick succession of explosions.

"In a matter of seconds, it turned into night," Abu al-Qumssan said. "It felt like containers of explosives and iron were dropped on us. It was a very strange and bloodcurdling sound."

Israel said it targeted a Hamas command center in the camp. Videos, including one filmed by Abu al-Qumssan, showed deep craters and destroyed buildings as far as the eye could see.

"I couldn't make out the streets from homes," he said. "People and bodies evaporated."

He went to his uncle's house, only to find the flimsy metal structure had been crushed into nothing.

Airwars identified 112 civilians killed in Jabaliya that day, including 69 children and 22 women. In all, 37 members of Abu al-Qumssan's family were killed in the shack and two nearby buildings, including four of his cousins, his aunt, her daughter and granddaughter, whose bodies were locked in an embrace.

Of the 10 strikes analyzed by AP, it was the only one in which Israel named a commander. The toll on innocent Palestinians was immense.

The airstrikes left several craters, and weapons experts said they were likely caused some of the largest bombs in Israel's arsenal, probably 2,000-pound missiles aimed at tunnels, that are hardly used in populated areas.

Two weeks later, Abu al-Qumssan's own house, only several metres from the large explosion, was bombed. His wife, 5-year-old daughter, mother, two sisters and 10 other relatives died. He and his three sons survived because their upstairs room caved into the crater.

Abu al-Qumssan called his daughter Nour's name over and over.

"My friend pretended to be trying to save her to calm me down," said Abu al-Qumssan, who as a journalist has a rare phone connection to send his images outside Gaza. "I knew she was not coming back and that she wouldn't be pulled out of under the rubble."

In all, 55 members of his family perished in Jabaliya in two Israeli bombings two weeks apart. By the spring, the family managed to document at least 82 killed, most in Jabaliya.

For the Okasha family, the killing of at least 33 members, including grandparents, children and grandchildren, in the Oct. 31 bombing "was a huge calamity. We are not a big family," said Abdeljawad Okasha, 61, who lives outside of Gaza.

By May, the family documented at least 57 members killed.

Brian Castner, a weapons investigator with Amnesty International, said any war crimes investigation in Gaza is complicated by the pace of the bombings, limited access for independent entities, and a lack of forensic evidence. Since October, Amnesty has found evidence o f direct attacks on civilians, unlawful and indiscriminate attacks in at least 16 Israeli strikes it investigated that killed 370 civilians, including 159 children and "decimated families." The strikes included three as recent as April.

The last bombing analyzed by AP hit the Maghazi refugee camp in central Gaza on Dec. 24.

Mohamed Abed, a journalist who arrived soon after the strikes, said three explosions came less than an hour apart. The first decimated the Musallem family. The second hit the same road and killed several members of the Abu Hamdah family, including a drama teacher. The last hit a house further away.

A total of 106 people were killed from at least eight families, according to handwritten hospital records that listed the numbers from each family, obtained by the AP. The UN had earlier tallied 86 dead.

Israel said it was going after Hamas militants and "mistakenly" struck two adjacent targets. The statement is the first and a rare one in which Israel acknowledged an error and expressed regret for the "injury to those not involved." A military official told Kan, the Israeli public broadcaster, that the wrong weapon was used.

The line between military necessity and disproportionate civilian casualties is "based on the good faith judgment of the commander making the decision" said Geoffery Corn, a former Judge Advocate General officer and director of the Center for Military Law and Policy at Texas Tech University. "That line is incredibly amorphous."

In all, the AP record included 2,700 killed from over 70 families, with some previously unknown details on their deaths, such as where they were killed or who died along with them.

"Everything we build vanishes"

Kinship reaches far beyond the nuclear family in Gaza. Compounds, frequently multiple buildings of three stories or more, are occupied by an entire bloodline.

Extended family is an independent economic unit, and relatives pay each other's debts, pitch in for schools. Often, a family lends its name to a block or even an entire neighbourhood. And when formal governing structures are contested, families in Gaza usually step in as enforcers of order -- or sources of violence at times, said Ilana Feldman, anthropology professor at George Washington University, who studied the history of rulers of Gaza.

When the Salem family home in northern Gaza was destroyed in 2009, Youssef and his brothers chipped in to rebuild it for their father and uncles. It was damaged again in 2014. Now it is a skeleton, torched from the inside.

"Everything we build vanishes with any escalation, any war," Youssef Salem said.

After the 2021 war, he told his wife it was time to leave with their toddler daughter. He found work as a legal analyst in Istanbul and begged members of his extended family to join him. He took a little bit of Gaza with him -- his books, his traditional checkered kuffiyeh scarf. His wife packed wedding and family photos and her favorite trinkets.

After Oct. 7, he took advantage of the safety of exile to coordinate for relatives in Gaza as they chased shelter and food. He connected them to one another and kept them updated with the news.

"I left Gaza, but I still belong," said Youssef Salem, who told AP his family story over a series of telephone interviews.

On Dec. 11, the square that carries the family name was brimming with 150 relatives, some displaced there and others who came for the funeral of two of their own, killed in an earlier strike.

Battles had been raging between Hamas and Israeli forces for days about a half-mile (kilometre) away. Just before dawn, airstrikes hit the Salem compound. The explosions knocked down one building, leaving a pile of debris, and sheared the facades off several others.

Survivors deny any fighters were in the compound. Videos showed men clawing through crushed concrete to remove the bodies of men, women and children. A donkey cart waited at the top of the street to transport the bodies.

Sufyan Salem, a second cousin to Youssef, survived only because he had given over his apartment to visitors and was sleeping down the street. Among the 80 Salem family dead: his mother, three brothers, his only sister and her four children. At least 27 are missing beneath rubble that has yet to be cleared away.

"Those who left us are the ones who received some comfort. The survivors are longing for relief," Sufyan Salem wrote on Facebook.

In Istanbul, Youssef Salem updated the spreadsheet.

Three days later, most of the surviving Salems followed orders from an Israeli pamphlet dropped from an airplane to head to the Rimal neighbourhood. More than 200 people were crammed inside the abandoned two-story villa, mostly women, children, and the elders. They raised a white flag above the home.

Israeli troops i n Rimal were establishing bases and set up snipers on roofs. A curfew was in place for four days. The sounds of combat echoed from an adjacent neighbourhood.

Munir, his uncle, snapped a reassuring photo of the men playing cards, a family tradition. They even secured coal for their water pipes.

On Dec. 18, Israeli tanks rolled in, tearing down the fence and ordering the family out. Mohamed Salem, Youssef's 21-year-old cousin, overheard Munir and other men of the family, who spoke Hebrew, refusing to leave.

It was the fourth time they'd been ordered out of a shelter, and they said nowhere was safe. Besides, they argued, the Israeli army controlled Rimal.

Mohammed Salem slipped out to fetch water for another cousin, who was pregnant, and Sham, a baby girl born during a brief truce in November.

Shortly after midnight, Mohamed Salem, standing on a building across the street from their villa, counted four direct hits from airstrikes. The villa collapsed, and bodies were flung outside.

With snipers and soldiers everywhere, he didn't dare approach until daybreak brought an end to the Israeli curfew and he and a cousin watched tanks roll over relatives half-buried in the debris. It took days longer to pull out the decomposing bodies of his uncles, Saeed and Munir.

"There are bodies in the ground still. No one can reach them yet," Mohamed Salem said.

He said from the house packed with more than 200 Salems, only 10 are still alive. Nine-year-old Abdullah is the only survivor of his bloodline -- Israeli strikes killed his father, mother and seven sisters. In May, Mohammed Salem survived two strikes on his home that he returned to in north Gaza. Seven family members perished.

Of Gaza's 400,000 families, none has been spared, said Omar Shabaan, an independent researcher and economist from Gaza, hurting Gaza's society, history, and future.

"Everyone is targeted; families from all classes, poor, Bedouins, farmers, businessmen, wealthy people who are nationalist but unaffiliated with political action. There is no distinction," said Shabaan, whose family counts many dead, including nine women. "It is becoming clear that this is a targeting of the social structure."

People of Gaza will be preoccupied for months after the war ends with looking for their missing and removing those under the rubble, Shabaan said.

"If they find the bodies, they will start going after the paperwork. They will start looking for papers to prove them as humans: Their death and birth certificates, their graduation papers, their land or home deeds," he said.

By June, the Salems' effort to document the toll was coming apart. Yousef Salem despaired of counting his family's dead. His cousin who took over the spreadsheet was critically injured in a strike.

"When the family had one martyr, it lived in grief for all its life. Imagine now," he said, his voice cracking. "How could we still be sane after all of this?"

Now he just calls his mother in Gaza every day to make sure she is still alive.

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Wafaa Shurafa in Deir al-Balah, Gaza, Kareem Chehayeb in Beirut, Lee Keath in Cairo, and Samya Kullab in Baghdad contributed to this report.