If it doesn't bother you and it doesn't bother him, who cares. My brother and I have been seen each other nude forever. Hey, he's my brother. When we both started to sexually mature, , he asked to see my vagina, and I showed him. But he was just curious. Of course, guys have their parts hanging out, so I have seen them many times, especially because he sleeps nude and doesn't bother to dress until after he showers.
I was a little self-conscious when I developed breasts, especially because mine were so much smaller than my younger sister's chest. But I got over that.
I only saw him with an erection one time. I had a friend over swimming, and she wore a loose bathing suit. She made it a point to show off, not to mention rubbing against him when swimming in the pool. When we came in and stripped off our bathing suits (just my brother and I, my friend changed in a separate room) he had an erection. I didn't say anything. (They went on to study in his room, and...)
I visited him recently in college a short while ago, and stayed in his room. I changed clothes with him right there in the room.
There has never been anything sexual between us. Just make sure it is that way between you and your brother.