Couldn't resist that title

I'm hoping that somebody can help a poor muddled country bumpkin researcher.....
I'm stuck out here in Suffolk trying to solve a mystery.
I have Nathan Adams b c1811 in Battersea as a direct ancestor
He is on the 1851 census married to Mary Ann who was born in Paris
They have six children including Joseph who is 11 months, and Nathans mther Martha living with them.
I can't find them in the 1861 census at all
By 1871 he has a different wife - Jane born c1826 in St Dunston - and four children, only one of who appears to be one from 1851 - Joseph. One of these children is Sophia, who again is on my direct tree. As she is 18 on this census I really need to know whether she is a daughter of Mary Ann or Jane.
I can find no births marriages or deaths for the principal characters in this little drama, and would really appreciate any help that anybody here can offer. Frankly I don't know where to start !
Part of me would love Sophia to be the child of Mary Ann, as it looks possible that she could be a baby born from a trophy bride taken at Waterloo, which would be very romantic - but on the other hand it means my tree probably stops dead in France !!