It's a problem parents of every generation have had to face: What do you do when your children start asking if Santa is real?

Seattle-based author Martha Brockenbrough was faced with this very dilemma six years ago, when her nine-year-old daughter Lucy asked her for the “truth” about Santa. 

Brockenbrough, who at the time was writing for the parenting website Cozi, came up with a heartwarming letter explaining the "truth.” The letter was published online, and has since gone viral.

She agreed to let CTVNews.ca publish the letter here below, so that readers may also use it if they like. 

'A love letter to my child'

Brockenbrough said that even though Lucy is now 15, the letter still holds a very special place for her family.

At the time that she composed it, she and her daughter – who is dyslexic - had been writing letters back and forth to each other.

"I wanted to find a way to encourage her to write and ask anything, and I would always write a reply," she told CTVNews.ca, adding that she had already taken to writing short notes to her daughter as the Tooth Fairy.

But one day, Lucy saw a partially written letter from the "Tooth Fairy" on Brockenbrough's computer. Shocked, she wrote to her mother and demanded to know the "truth," on whether or not she was also Santa.

"She had been kind of asking about it for a while," Brockenbrough said. "But when she put the 'TRUTH' in all capital letters, I knew I had to tell her.

"When a kid asks for the truth, you cannot give them fantasy. So I sat down to write a reply, and this just sort of emerged."

The mother of two said that when she sat down to write the letter, she simply thought about her feelings on family, love, giving and gratitude and let the words flow from there.

"It's what we give to each other, and all the love and thought and care we show," she said. "It's not all about presents, as much as it is learning to believe in the magic of the world, and us to take care of each other as humans."

Once the letter went online, the response was immediate, Brockenbrough said, noting that most parents seem to really love it.

She attributes its success to the fact that it is honest, but doesn't crush the fantasy for the child.

"We want to tell our children the truth, but we don't necessarily want to make the world seem empty of magic," she said.

Natalie Coulter, an assistant professor of communication studies at York University, said part of the enduring legacy of Santa Claus stems from our desire to keep the magic of Christmas alive for our children.

"I think it's really nostalgic for us to think about the fact that our children have these romantic notions of fantasy and imagination," she told CTVNews.ca. "There is a really beautiful side to that -- that children still unquestionably believe in this benevolent person."

However, when your children do start to ask questions about the veracity of Santa, Coulter said parents can open up the discussion to talk about the general importance of charity and generosity.

"When your child starts getting older, you can involve them into being part of that magic, and that pleasure and generosity of giving," she said. "And now that they know about Santa, they can be part of that pleasure."

Coulter noted, however, that parents should explain to their children that every family has different beliefs about Santa, and that even though they are now in on "the secret,” they shouldn't tell their friends.

"It's not their job to tell other kids," she said. "That's a way to continue with the spirit of Santa, to believe in that joy and pleasure. And if you're telling people before they're ready, you're taking away that spirit and belief."

Meanwhile, Brockenbrough's letter has been so well-received that she has agreed to publish it as a children's picture book, which is set for release in 2017. However, she notes, the letter was never intended to come out as book.

"It was really just a love letter to my child," she said, noting that her younger daughter, Alice, also eventually asked for the "truth" about Santa.

Brockenbrough’s older daughter Lucy, now 15, says that at first she was angry that her younger sister was told the truth about Santa, as she hoped to keep up the “magic” of the story for longer. However, she’s happy she and her sister now get to participate in new holiday traditions.

"It's hilarious that my mother doesn't even try to hide the presents now," she said in an email. "Now, Alice and I can contribute to present buying and choosing. I honestly think it makes everything a whole lot easier."

The letter:

Dear Lucy,

Thank you for your letter. You asked a very good question: “Are you Santa?”

I know you’ve wanted the answer to this question for a long time, and I’ve had to give it careful thought to know just what to say.

The answer is no. I am not Santa. There is no one Santa.

I am the person who fills your stockings with presents, though. I also choose and wrap the presents under the tree, the same way my mom did for me, and the same way her mom did for her. (And yes, Daddy helps, too.)

I imagine you will someday do this for your children, and I know you will love seeing them run down the stairs on Christmas morning. You will love seeing them sit under the tree, their small faces lit with Christmas lights.

This won’t make you Santa, though.

Santa is bigger than any person, and his work has gone on longer than any of us have lived. What he does is simple, but it is powerful. He teaches children how to have belief in something they can’t see or touch.

It’s a big job, and it’s an important one. Throughout your life, you will need this capacity to believe: in yourself, in your friends, in your talents and in your family. You’ll also need to believe in things you can’t measure or even hold in your hand. Here, I am talking about love, that great power that will light your life from the inside out, even during its darkest, coldest moments.

Santa is a teacher, and I have been his student, and now you know the secret of how he gets down all those chimneys on Christmas Eve: he has help from all the people whose hearts he’s filled with joy.

With full hearts, people like Daddy and me take our turns helping Santa do a job that would otherwise be impossible.

So, no. I am not Santa. Santa is love and magic and hope and happiness. I’m on his team, and now you are, too.

I love you and I always will.

Mama