Riku HAD a pair of pajama pants, he just didn't wear them often. They were mostly reserved for late-night-movie-and-pizza-parties with Kairi and Namine and in the morning when he finally made it downstairs to have breakfast with his moms.
"You know, that goes both ways," Riku pointed out. He had significantly more naked Sora time too. Living together was going to be awesome like that.
Riku looked over at Sora to see if he was serious, and pulled Sora up off the bed by the drawstring on his pants. "Do you really think I'd ever get sick of you? Alright, we might drive each other a little crazy," it wasn't going to be perfect, he was kinda aware of that, "But we'll work it out. That's just part of living together." Really, he'd be more concerned about Sora getting fed up with HIM. Have YOU ever tried to live with Riku?
"And since we're going to be together forever," Riku pointed out, "Its good that we're working all these little things out now."