I dont believe the comma was necessary in your sentence. Also im pretty sure he was just trying to get them to stop in a weird way

I don't believe you should be correcting other people's grammar when yours looks like that.

He may have heard them, and his comment may have made them awkward enough to stop.

"And kept going". Clearly not awkward enough.

I assumed the brother was being sarcastic, trying to get them to stop or be more quiet, and the boyfriend didn't take the hint. If I'm wrong, then that's super creepy.

If he keeps going that way then pretty soon he'll be begging to join in.

@iShanny You could be right but the boyfriend saying "Sure" may not be that he didn't take the hint. It may simply be that he doesn't care. Why should they bother quieting down when the brother already knows what they are doing? Realistically, since it's their house, why should they quiet down at all. If the brother doesn't want to listen he can turn up the television, play loudish music, put on headphones, or go elsewhere for a little while.

Losing*