After coming out as gay to some people, they will sometimes feel the urge, as part of a bonding process and demonstration of acceptance, to confide something back in you. This often consists of "I've thought about it myself", or "I've got a gay mate / brother / hat". One of my flatmates, however, came back with the revelation that he'd slept with his brother, which initially didn't bother me, until he elaborated that they'd done it recently, that his brother was around eight years older than him, that he'd enjoyed it, and that there nothing stopping him from doing it again. I still didn't really mind, as my laissez-faire morality saw that they weren't going to breed monsters, so they're not harming anyone. So, I kept quiet until my flatmate insisted that we should meet each other. Why that would have been appropriate, I cannot guess. Perhaps his brother had been complaining about how he never gets to shag anyone except the family, and fancied a change.
Well, fuck me if he didn't look like Bob Carolgees. My tolerance collapsed - it was all too much for me. Even my slack, slack morality couldn't tolerate shagging Bob Carolgees. I told everyone I knew, and felt immediately better for it. A secret shared is a secret halved - by the time I'd finished, the individual portions of secret were microscopic.
But no less sweet. It's not every day you get to betray a confidence so humiliating.