Hello! I've been looking for this yaoi manga and don’t remember all the details, but this is what I got:
I think it takes place in an all boys school. Guy A is really cute and looks all innocent. Guy B is his childhood friend and he always tries to protect guy A from getting hit on by other dudes. Guy A is actually not innocent and is somewhat annoyed that Guy B is cockblocking him lol. Then there is Guy C who I think was on the student council with Guy A. Guy C pretends to like Guy A and Guy B offers up his body instead so that Guy A will be left alone. Of course Guy C liked Guy B all along but Guy B was too dense to notice. They get together in the end.

I will be eternally grateful to whoever can point me in the right direction!

Hi! I found a manga, some details are different (Guy A and B are twins, A isn't annoyed at B, he's annoyed at the guys who's after B because he loves him - and yes they're brothers, but the main theme isn't incest) but I found some similarities with what you described so I'll give it a shot. Maybe it's Innocent Maze?