Not happened yet, this is hypothetical. It comes from a conversation with a male colleague at work, (for the record he is 29, childless, and very right-on).
He was saying that if his partner did not tell him when their imaginary future daughter started her periods, he would be gutted.
I argued that if a child has specifically requested that you 'don't tell dad' then you shouldn't as it is her body and her privacy?
In my case, I could imagine very well my dd saying that and actually I don't think it would be a huge deal for my partner as he would respect her privacy, but I am thinking it through now a it is probably quite imminent.
But AIBU? The male colleague was horrified, and said that a mum and dad should be absolutely united on everything and that means absolutely no secrets whatsoever.