Regulus and Sirius' strange relation

Sirius drug Regulus to the Potters' when he decided to leave. Quite against his will. In a different household, he has to attempt to adapt to the strangeness of these new people. On the bright side Barty has decided to be his supportive if stubborn self, and has practically invited himself to stay for the duration of Regulus' stay.As for James, he doesn't know why, but for some reason, Sirius seems...different. Perhaps it is because he can see the real relationship between the Black brothers, or maybe it is that he is actually getting to know Regulus, rather than getting to know him through what Sirius says about him...or maybe it was both, but seeing it brings a bad taste to his mouth, and a difference in how he sees his best friend.Remus doesn't know what to think...but recently seeing how Sirius talks and acts with his brother has left him questioning everything he knows, and there isn't a single soul he can tell...except maybe the person making him question what he knows about his boyfriend.Sirius is frustrated. He saved his brother from their parents and yet he is still being incredibly ungrateful. He really just doesn't know what to think or do about it, and it is the most frustrating thing.