My wifes cousin (male) saw me in my briefs. We were being fitted for tuxes for my brother in laws wedding. He has made several comments to me that he wears the same kind that I do. I saw him undress and I know that he does, and even though he is of legal age, I feel awkward talking to him about it since he's family. If it were anyone else, I would seriously indulge.
I'm pretty sure that he took a pair of my underwear. He had sent me a message telling me that he thinks a pair of my underwear wound up in his bag when he stayed with us one weekend. He has asked me to prove that they are mine and I can get them back. I told him that I can't imagine how mine would have been in his bag, but feel free to keep them.
I've taken underwear from guys, and if he wasn't related, I would have taken his. But I just can't do it. I like him, he's a cool guy, but I don't want anything further than that with him. I wish he had not seen me in my underwear. Lol.