I am not sure if I am the only one but in 50 years I am not able to get right how to sit without having my genitals in the way, and having to use my hands (often under my trousers, always discreetly) to positioning them out of the way. Doesn't matter what kind of underwear I am using: loose boxers are the worst, but boxer briefs or briefs have the same effect...
Trying to use those more often, and probably will buy more, I really see the difference with loose boxers in terms of not worrying about my sex. I used to wear loose boxers because of fertility issues, but that's something I do not have to worry.
Testicles are normal size (I think), penis is larger than usual, I always felt it pushed down all between my legs when seated.
