When I was 14, my parents informed me that I had a half brother. He was my father's son by another woman. My parents were already married when my brother was born, but I hadn't come along yet. It was a huge scandal when it happened. My half brother came to live with us after his mother died. He was 16. My half brother got me pregnant. He didn't rape me; I wanted to have sex with him. Everyone in the family found out — huge scandal number two — and it took me years to get over it and stop blaming myself.

Now I'm 26 and engaged. What do I tell my fiancé? My parents wound up divorcing — my mother called the police on my half brother and tried to physically prevent me from getting an abortion — and I don't speak to her anymore. But my father and brother are still in my life.

I get panic attacks when I think about having to tell my fiancé about any of this, Dan, because I don't want him to see me as sick. But if I don't tell him, he'll hear about it from someone else. What do I do?

The Sister Act

"This could happen to anyone," says Debra Lieberman, assistant professor of psychology at the University of Miami.

A quick clarification: Lieberman means this could happen to anyone who meets a sibling under similar circumstances.

Coresidence throughout childhood — particularly early childhood — creates sexual aversion in adulthood, explains Lieberman, who has studied "sibling incest avoidance" extensively. It's a phenomenon called the "Westermarck Effect," and it doesn't just affect biological siblings; adults who grew up in the same home experience the same feelings of sexual revulsion.

"TSA and her half brother were not raised throughout childhood together and neither observed his or her mother caring for the other as an infant," explains Lieberman. "These are the two cues that have been shown to lead to the categorization of another as a sibling. When these cues are present, strong sexual aversions tend to develop. Without these cues, no natural sexual aversion will develop."

(What this means, of course, is that everybody who read TSA's letter and thought, "What a sicko! I would never fuck any of my siblings!" needs to back the fuck off. If your parents had surprised you with a long-lost sibling when you were 14, dear readers, you, too, could be facing an extremely awkward conversation with your fiancé. There but for the grace of God, etc.)

So what, if anything, should you tell the man you're about to marry, TSA?

"If it were me," says Lieberman, "I would probably say something. I would explain the situation and the science. Unfortunately, this might gross out her fiancé, especially if he has sisters. But living with this stress" — the fear that he'll find out at some point — "does not seem like a happy life."

I'm a 23-year-old female in a monogamish relationship — thank you for that word! — with my wonderful boyfriend of two years. I moved away last year to attend graduate school, and we agreed it was okay to sleep with other people while we're apart. The last person I slept with was an acquaintance who knew both of us and understood what the deal was with our relationship. My question is, if I'm just looking for casual sex or a one-night stand, should I make it clear that we're just going to have sex and I'm not interested in dating?

Full Disclosure Necessary, Yathink?

If you meet a guy in a bar, exchange four words with him, and you wind up back at your place, FDNY, the person you're about to fuck can reasonably make two assumptions: (1) you're a slut (in the sex-positive, reclaiming-that-word, sisterhood-is-powerful sense of the term), and (2) he's unlikely to see you again. Under circumstances like these, FDNY, you're not obligated to disclose your relationship status. The only things you're obligated to disclose are how much clitoral stimulation you require and the time you'll need him out of your apartment.

But if a nice boy asks you out on something that your parents and steampunks call a "date," and he explains that you're really, really special, and he refrains from spitting Jäger shots into your mouth, you are obligated to disclose your relationship status to him, lest he make the entirely reasonable assumption that you're single and interested in him, too.