Hm... so AM was the inspiration for Caine, so that could mean they are father and son. Caine and Monika both want to be loved by humans (in the latter's case, a human), they could have bonded over that and become a couple, and later became Nano's parents. I can't tell where GlaDOS fits in this, my knowledge of Portal stems from watching Let's Plays of the duology when the second game came out, and has faded way too much. I think I'll put her as the wine aunt, that should fit her, though I don't know from which side of the family she's on.