My DD is spending Christmas with her dad this year; we alternate years, and I'm fine with that (been enjoying some 'us' time with DP) but I've just spoken to DD on the phone and I asked her in a lighthearted way 'did Santa come?' to which she replied 'Dad told me that he doesn't exist' 
Shes 11, so I know she doesn't believe - but I don't ever remember my parents 'telling' me - it was part of the fun of Christmas, pretending to believe 
I know she'll play along for DSS when we 'do' Christmas next week - but I'm sad that her dad has taken that fun away, it seems a shame 