Regulus and Sirius were always the type to need someone to sleep beside when they couldn't sleep beside each other.
After a couple of months in the dorm with the marauders Sirius had stopped asking if someone would share a bed with him. Every night when they were getting ready to sleep, Sirius wound up in Remus', Peter's, or James' bed and they never fussed over it, just accepted that they were going to share a bed with a cuddle monster (none of them minded the cuddling no matter how much Remus and Pete complained). (Of course as wolfstar became a thing, Remus always dragged Sirius to his bed unless he knew Sirius needed Pete or James.)
Regulus was very different in the matter. He never asked, he would rather stay up through the whole night or wake up constantly because of his nightmares than be the one to ask or do. Evan and Barty secretly discussed their worries with one another about Regulus' lack of sleep or constant thrashing in the night but thought best not to question him. It wasn't until Regulus had fallen asleep very peacefully on Evans bed (that Evan happened to be laying on as well) for a full eight hours in the middle of their second year that Barty and Evan decided that no matter what, one of them were going to force Regulus to share a bed with one of them. Reg put up a good fight against it but he was so grateful to them. He was so grateful that Evan and Barty both liked to hold on to him in the night because it grounded him, reminding him where he was at and who he was with, just like Sirius had done for him.
(Even before Rosekiller got together, all three of them shared a bed here and there. It started as an accident with Evan falling asleep on Barty's bed with Regulus and Barty already on it. Regulus didn't even attempt to get up so Barty planned to move to one of the other beds but as he was getting up to leave Evan dragged him back down beside him (so much for being asleep) and so Barty stayed, and they all decided that it wasn't so bad sharing a bed with three people. When Rosekiller did get together and wanted alone time, Dorcas was already happily waiting for the late night conversations that she and Regulus happened to always fall asleep having and he had James to sneak off to either to the come and go room or to James dorms (yes Sirius was very much aware and would make a fuss about it.))
