But... if he and Sam have never promised or even talked about being exclusive, is it unfaithful, really?
Oh dear, now your Remus rationalizations are toying with my head! O.o I suppose you're right, although it doesn't seem right since they're making proclamations of love to each other and neither actually said they would see others either. *sigh*
I can't remember does Remus come out and actually say "I love you" to Sam? He says "I love you too" Which in my mind isn't quite the same because he seems to hesitate every time he says it. I wonder if Remus is afraid to get close to Sam because of all his previous losses and is substituting Teddy because he's already close to him? Maybe Remus doesn't like the idea of growing old, and here's this really attractive young male who's interested in him. That's a stroke to the ego.
And I want to know if Sam every finds out and what's going to happen when he does? O.o And what happened to Sam before that's made him so leery of being in a relationship again?
So many questions it's killing me and this is story is 22 chapters long! Excellent job :)