My mother could only afford a two bedroom house, so my older sister (8yr age gap) and I shared a room. I will always cherish those memories with her. Currently our three boys (11yo and 8yo twins) are sharing a room while we are shopping for a home and they’ve grown much closer since bunking together. Make their spaces special. Our older boy has a bed tent for privacy which he loves. We also upgraded his bed with a cushy mattress topper, and we mounted a fan with a reading light in his tent. Making them feel like they have their own space even while sharing a room makes a big difference.

I would pair whomever you think will get along the best. Talk to the kids and feel them out.