Sam existing at all
It just feels tacked on in a way.
I mean, I know part of Sidney and Billy's whole thing was she was "sexually anorexic." And it's not like I think he was so in love with her he wouldn't cheat.
It's more like Voldemort and Bellatrix having a kid. I don't believe it because I feel like Billy was too preoccupied to bother with an affair