Just so we're clear:
I do not own Harry Potter or these wonderful characters. If I did, the books would be a bit different. Don't sue me.
This is indeed slash, which is a gay relationship. If for some reason you don't like that, don't complain to me. I warned you before hand, so deal or just don't read.
Sirius lay on his back, Remus' head on his chest.
"Remy?"
"Yah Siri?"
"I think we should tell him."
Remus bolted upright. "What?"
Sirius sat up as well. "I think we should tell Prongs about us. We've been together for a few months now, they know nothing so far, and they're our friends. I think they should know."
"But what if they think it's gross? And ignore us? What if they hate us?"
"They won't."
"How can you know?"
"Fine. How about this. We get them into a discussion about gays, and ask them what they would do if, hypothetically, we were gay. Or even together. Then we'll have our answer, and tell them or not, depending. Alright?"
"Alright." Remus settled back down on Sirius's chest and fell asleep.