The singer was chatting about the family’s Christmas plans in an interview with People, where he said: “Luna, she talks about Santa and I don’t know if she really believes in Santa or if she just does it to play along with us.
“I don't know what's going on yet. I was never raised on Santa as a kid, so I never knew about the way parents keep up the mythology for a while.”
But despite suspecting their little one may know the truth, the family are going to keep the traditional myth going for now.
“So I don’t know how to play this out with Luna, how long we're going to keep the charade going,” he said. “I feel like she’ll figure it out pretty soon.”
John and Chrissy aren’t alone in not knowing when or how to discuss the existence of Father Christmas with their children.
A recent survey has found out that children stop believing in Santa aged 8.
The poll, by Tilly and Jasper, revealed that a fifth said their little ones found out when they were 8 years old, while 17% said they found out when they were just 6, with age 7 being the third most popular age to find out Santa was fictional.
While the magical myth is an essential part of our childhoods, an essay published last year questioned whether the age-old tale of Father Christmas could actually be damaging to kids?
The paper, called “A wonderful lie” and published in the journal Lancet Psychiatry, suggests that the trust children have in their parents may be undermined by them spinning stories about Santa.
What’s more, the reasons behind maintaining the belief could actually be morally suspect.
“If they are capable of lying about something so special and magical, can they be relied upon to continue as the guardians of wisdom and truth?” the researchers write.
“If adults have been lying about Santa, even though it has usually been well intentioned, what else is a lie? If Santa isn’t real, are fairies real? Is magic? Is God?”
But not everyone believes that not revealing the truth, that *spoiler alert*, Father Christmas isn’t real, is damaging to children.
“Parents often think they have to be black and white with this - yet they don't,” says Jane Evans, The Lasting Life Change Coach, and an expert in parenting and childhood.
“Children are often exploring their world, so let them explore.”
Evans suggests that if a child finds joy in believing in Father Christmas parents could help give them permission to believe.
“I believe many children have an inkling early on about it not being real - however they often want to believe and they want to keep their parents happy by entering into the spirit of it,” she says.
“With my son I used to say, when he asked me questions, ‘I still 'like' to believe that Father Christmas may be real so it's really exciting to see what might be under the tree on Christmas Day....’
“For most children that kind of response is enough,” she adds.
For total non-believers Evans suggests telling your child it is fine if they don’t believe, without making a big deal out of it.
“Don't confirm their lack of belief as you could be shattering their dreams,” she adds.
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When to have the Father Christmas discussion
According to Dr Nick Smith, principal of Oxford Home Schooling if your child has already started to question Santa's existence, this is a good sign that they are having doubts and are able to separate fact from fiction.
“Let them know at this moment - it's not helpful to lie,” he suggests. “They're clearly open to the idea that he might not be real, so they will be better prepared to hear the truth.
“If years go by and your little one doesn't approach the subject themselves, then you'll have to initiate the talk,” he adds.
Certified child play therapist Amanda Seyderhelm agrees that the right time to start the discussion is when your children start asking questions about whether Father Christmas exists.
"When they they ask you if it's true, that is the 'natural' time to begin having the conversation with your child,” she says.
“But do so carefully. Remember that the spirit of Father Christmas is associated with fantasy and wonder for children so, which is a glorious thing, so don't be too quick to shatter this!”
How to break the news
Emphasise the Christmas positives
Just because there’s no Santa, doesn’t mean there’s no Christmas. Dr Smith says that it is important to stress there are lots of positive aspects about Christmas that still happen once the concept of Father Christmas is removed.
“Chat about the decorations, the presents, maybe the religious origins if that's what your family would like,” he suggests.
“This will help your child realise that Christmas is about so much more than St. Nick and hopefully they won't take the news as hard.”
By helping children embrace the generosity of Christmas. “Encouraging your child to share gifts, will help them learn about the true spirit of the season and they will start to feel the joy of giving. This can help to fill the void left by Father Christmas,” Dr Smith says.
“Every child will react differently to hearing the news about Santa - some will already know, some may be surprised and others will be sad. But it's best that they hear it from you, rather than someone at school or another child who may be seeking to spoil their fun.”
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Encourage them to keep it to themselves
News spreads like wildfire in the school playground especially about something as important as the existence of the big man. So, Andy Barr, co-founder of online price tracking website Alertr suggests trying to ensure children don’t immediately run off to share the spoiler with their friends.
“Young children all mature in different ways and at different times, and some parents might be pretty mad that they've not had the chance to have the conversation themselves,” he says.
“Others might be different in their parenting style and want to keep their child believing in Father Christmas for as long as they can.”
Open up a discussion
For those parents still not sure if breaking the news is the right thing to do, Evans suggests trying to switch the direction of the conversation.
“If your child comes up to you and says ‘I don't think Father Christmas is real’ say something like ‘oh my goodness so how does it feel when you think that Father Christmas may not be real?’” she suggests.
“That takes the conversation off in a new direction where they explore their feelings without you coming down on one side or the other. However it opens a discussion. Be curious with your child rather than dictating,” she continues.
“Remember what Roald Dahl said - if you don't believe in magic, you'll never find it.”