my dh's family also don't bother with our dds (or us much)
dh and his first wife split up long before I met dh - he has two children form this marriage.
dh's brothers both see my stepchildren (who I get on well with, and who love their younger sisters) as somehow "more" related ot them than my (and dh's) dds. His older brother has not even bothered to meet the dds (they are 6 and 3), and the younger brother has said it was "inappropriate" for dh to have more children.
dh's parents are also not that bothered - they struggle with dd1's disability (as, I suspect, do his brothers).
It is very hard to see your children ignored year after year, and equally hard to try to help dh through it.
he is increasingly fed up with his family's games, but at the same time, they are his family.
we were recently not invited to his brother's 50th birthday party, while dh's ex was invited. dh was, quite rightly, very upset by this.
the whole thing is, for him, turning into him having to choose between his family and us (me and the dds), without there being any reason for him to have to make this choice...