Thudpucker, does May state that Mary is her sister in USM? Guess I don't recall that (typo? ha ha). I remember later like the Clone Saga her saying "you Parkers." I guess I always assumed Ben and Peter's father were brothers and left it at that.
OK now I'm going to read that Wikipedia entry and likely answer my own question ...
I'm not a big Spider-man fan, I'm still not. But I love the work Bendis is doing with Peter and especially with MJ. He finally won me over to the point I want to own this series and re-read it all every few years.
When May is telling Peter about his parents stuff in the basement she says that Peters Mom was her sister.
Every story ever told has hanging threads.
If you pull at them, you're only going to hurt yourself.