I don't watch the show and don't happen to have any incest pairings that I ship in any fandom (and hell, I don't have any siblings either), but I think it's fair to point out that not every sibling relationship is exactly the same. The way siblings relate to one another can be hugely affected by birth order, gender, age gaps, the presence/absence of other kids around, individual personalities, and a million other things. What you see as "just being brothers" could come across very differently to someone who has a different relationship with their siblings.