L.C.
Wow, that would be a stunner. I would be stunned. Not disapproving. Not unsupportive. Just gobsmacked. It wouldn't be a matter of my brother being gay being good or bad, right or wrong. He is who he is. It's just that I would be shocked that I could know him and love him and not know this really important thing about him. I would also be sad that he felt he had to be anything other than himself for so long.
You have to look at him differently in that he has something about him that was different than you thought it was, but that doesn't mean you have to love, communicate with, support, enjoy or treat him differently. If you are not, and it sounds like you aren't, then you are absolutely supporting him.