The only time this happened to me, post-pubescence, was in the aftermath of a raging bachelor party. I was crashing at the groom's apartment and everyone except the groom and me had either gone home or was passed out. The drunken groom asked me very directly to show him my dick. I obliged, he joined me and we ended up JO together. (about 5 years later, after his divorce, he asked to blow me and, not being a fool, I obliged again)