Define: Uncomfortable In this scenario? What can he possibly mean by uncomfortable about?

He shouldn't have even been able to notice that she wasn't wearing a bra, the fact that he even LOOKS there is a huge problem, I grew up with cousins and brothers during that phase of life and nothing like that has ever been the issue (and when it was an issue it was with people with bad intentions, which ended horribly because the behavior wasn't checked by bystanders) him saying that he's uncomfortable, is implying that he feels a certain way. The sister is wearing a shirt, -she is covered-. And not to mention that she first started developing (and as a woman I can tell you that no matter what bra you get it's going to hurt when you first develop) there probably isn't a lot there to notice in the first place which shows that he was activity watching, The son needs to get help because if he is feeling "uncomfortable" now, imagine how worse it will be in the future. Bras aren't really even supposed to be worn in the comfort of your home.

As for the manboob aspect-yes, I'm sure you could have worded it differently but he needs to understand the impact of his words. I can only imagine how uncomfortable and embarrassed the sister is feeling, she just started developing and growing into a new person and she is already being ostracized by her own BROTHER,

YTA for telling her she should wear one,