I get the feeling this has been discussed before - apologies if it is old ground for anyone.
Have you moved to an area which is not your "home", or settled with a partner who is from a different part of the country, and found that you've, almost to your astonishment, raised children who speak totally differently from you? (i.e. from your personally, or from both of you?)
I suppose it's inevitable that children will pick things up from school. In our house I still find it odd and slightly jarring that my children have the "short Northern A" - DD will say "classe" and "grasse", and talking about going "oop" to school. And all three of them (DW, DD, DS) will take the piss out me for my Southern RP. (That is a "slightly irritated" face, not really "angry". Another new MN icon needed.)
I do know some fellow "southerners" at the school and some of their kids speak more like their parents than like their peers. I often mean to ask them how they do it!