?

I was at a house party with my boyfriend last week. My boyfriend s brother-in-law saw me dancing while my boyfriend wasn t around and literally out of nowhere asked me to cover my boobs. I was wearing a slightly revealing top (a vest top with jeans) that could have been pulled up to hide absolutely all boob. Also, this isn t the first time he s said this to me at other house parties. I felt embarrassed and kinda annoyed at the request so I just said that I was okay thanks. He didn t respond. But my question is why he asked me in the first place? My boyfriend would have said something if he thought what I was wearing was too revealing but he was comfortable with it so why wasn t his sister s husband?