Did your DP/DH tell your DSC's mum that you were pregnant - if so, at what stage in the pregnancy, and what were his reasons for doing so?
I have suspected for some time that my exH fiancée is pregnant - he proposed, they are buying a bigger house and have just bought a people carrier; and yesterday, my DP saw her and said that it was pretty obvious that she has a bump (although admits he's a bloke about these things so can't be sure).
My DD (11) hasn't mentioned anything to me about it - she does hold back on this sort of thing though; she eventually told me that her Dad/SM had got engaged several weeks after the event.
DD spends 50% of her time with her Dad, so it's going to have a big impact on her life; but I don't know if she knows yet or not, and until she mentions it to me, I can't say anything.