Please take the time to watch these two videos about Roblox :
https://m.youtube.com/watch?v=_gXlauRB1EQ&pp=ygUYcGVvcGxlIG1ha2UgZ2FtZXMgcm9ibG94
https://m.youtube.com/watch?v=vTMF6xEiAaY&pp=ygUYcGVvcGxlIG1ha2UgZ2FtZXMgcm9ibG94
Is your brother making games? If yes : there are several easy to use game engine like mentalo.app, Godot, gdevelop and such.
If your brother is mostly playing, then anything by Nintendo would be a good idea. Old consoles are cheap and if you have the Switch there are a lot of really good game on it.