Well, it depends:
Brothers: Moo (it's a nickname, and I'll probably want to hang out with him), my other brothers I have only met as an infant, so I'll definitely be rather shy but also wanting to learn more about them.
If they all were in the same room, it'll be awkward for me and Moo at first, but it'll probably dissolved by playing some video games.
If I was in the room with my sister, of course it'll be fun to hang out with her since I can see her. Maybe I can challenge her "skills" in games and just find something to do. She's a good older sister that I appreciate having someone to annoy with haha.
If she was there with my brother: It'll be some rival siblings in the room of "Who's Mom's Favorite" and shots (technically game terms) will be fired then.
If all my siblings were in the same room: I'll be so happy to see them all together for the first time, and I would love to hang out with all of them!