It was love at first sight, absolutely the craziest thing I have ever experienced," Melissa says. "The sexual force was like I was levitating off the earth. Your body instantly craves the other person." Acquaintances were always on their best behavior, but sisters loved each other enough to say anything.”—Lauren Weisberger

A hoped-for response from your wife might have been something along the lines of “I’m so sorry that this terrible thing happened. Thank you for telling me. I love you and want to support you in any way I can. Let’s talk about where to go from here.” When people don’t get that kind of empathic response from the person they’re closest to, they either futilely attempt to get the person to validate what happened or they simply retreat into their own denial (for instance, your idea to “let it go but keep my distance,” which isn’t really possible and puts you at risk of something like this happening again). Your sister is a jewel, a priceless, one—of—a—kind gem who makes living precious for many people, including you.”—Dave Pipitone Because all of these things occurred with other family members around, I did not feel like I could snap at her or push her away. I wish I had found a way to quietly tell her that she was making me uncomfortable and ask her to please stop, but I was still new to the family and not sure of myself with them. Also, she seems to have my wife emotionally bound to her to the point that my wife gets angry at the slightest criticism of her sister. My wife seems to alternate between being intimidated by her sister and feeling as if she has to protect her. That’s the best thing about little sisters: They spend so much time wishing they were elder sisters that in the end they’re far wiser than the elder ones could ever be.”—Gemma Burgess I told myself and others that I was so immersed in Teri’s care because no one else could understand Teri’s medical issues and advocate for her. Mom was a nurse, meanwhile, and had my dad, a radiologist, my brother, also a radiologist, and my aunt, a nurse, for support. But the truth was that I wanted to help and be with Teri more, and she wanted me with her, so I was. Whenever I thought about this, I felt equal parts warrior and betrayer.She is the mother I never had, she is the sister everybody would want. She is the friend that everybody deserves. I don’t know a better person.”—Oprah Winfrey We have our own, unspoken language—a look that makes one of us fall on the floor laughing or the slight inflection in our voice that conveys everything. It is the ability to prod laughter and love no matter how much your heart might hurt. Someone who sees you exactly as you are and thinks that is enough. Someone who will walk next to you always.”—Barbara Bush I gave real-life examples of teens who became pregnant or who contracted STDs even with the use of condoms; one of those persons was a close friend of mine. Husbands come and go; children come and eventually they go. Friends grow up and move away. But the one thing that’s never lost is your sister.”—Gail Sheehy Social scientists and psychologists have long researched how societies' prohibition against incest evolved: It's essentially nature's way of protecting humans from passing along the genetic mutations and disease risks that happen more commonly with close relatives, explains Dr. Debra Lieberman, a professor of Psychology at the University of Miami. The dominant theory, first proposed by Finnish social scientist Edward Westermark, is that people become desensitized to those they are raised alongside.

The news got even more startling: Before his affair with Melissa's mother and eventual marriage to Chris' mother, her biological father was married a first time — and Melissa had several half-siblings. "It was all so crazy. I was dumbfounded," she says. "My life was just exploding." Later that night, the pair separately scrolled through each other's photos on Facebook. As she looked at the images of Brian's life — as a musician, friend, and husband — unexpected feelings stirred. "I was confused. I was attracted to him. Then in bed, I started having actual sexual fantasies," Melissa concedes. "I thought, There is something wrong with me. Something isn't right."

But divorce is not an option right now. Melissa plans to get her daughters through the rest of their childhood in as stable and consistent an environment as possible. "But believe me, I want to leave," she says. "I struggle every day because my heart is with him. That's the most difficult part for me." Your sister knows everything to say to piss you off. But sisters tend to be each other’s biggest champion and also their hardest critics.”—Erin Foster All states in the U.S. have laws prohibiting marriage and/or sexual intercourse between first-degree relatives. In their state, it's a felony that's punishable by life in prison. Not only do Melissa and Brian feel their love shouldn't be forbidden, they also say they're part of a growing segment of society: As infant adoption and fertility treatments involving sperm, egg, and embryo donation increase, so will the numbers of people walking around who are unknowingly genetically related. Mom had steadfastly cared for my dad, my brother, and me since her early twenties. She rarely complained, but I thought I detected the toll this sacrifice took in the way she seemed happiest not with us, but at church or petting the dog or watching PBS. I tried to make things easier by hiding my troubles from her and sometimes even myself, but this time I was too weak to pretend. Sister. You are not only a strong woman, you are the strongest tie to the best years of my life.”—Melanie J. Pellowski

Life has its ups and downs, times of sadness and times of joy. You, little sister, have been through it all with me, thanks for being there.”—Catherine Pulsifer I wanted to inform my 14-year-old sister Kathy about something that I unfortunately just began to take seriously: abstinence. Sure, I have always known what the word meant, but I had never considered it an option for me, until recently. I felt that it was my responsibility to pass the philosophy of abstinence on to my sister because I know that she will not get it in the "going to do it anyway" program that is used at her high school. Also, she is a virgin (her friend is, too), so I wanted to show her how important it is to hold onto that purity. Parents are just parents, brothers are just brothers, best friends are just best friends, even husbands are just husbands, but sisters—well, sisters are the ones to whom sisters always turn in times of joy or trouble, celebration or crisis.”—Lorraine Bodger They claim their sexual and emotional connection is exceptional. "We have an innate trust and no boundaries with each other because we're family," Melissa explains. "When you get into a relationship with someone else, they're a stranger to you. Trust takes a long time to build. But because this is my brother, he's never going to do anything to hurt me."

We are sisters. We will always be sisters.Our differences may never go away, but neither, for me, will our song.”—Elizabeth Fishel