Apperantly this dude at 16 thought it wasnt a big deal
http://sports.espn.go.com/nfl/news/story?id=5497517
On May 9, 2003, Washington pleaded guilty to having consensual sex with his biological sister, Caylen. He was 16, she was 15.
"Incest," he says, looking straight ahead.
He says he didn't plan to do it. He was a teenager. Unstrung. Unsupervised. His world was at war. He was scared. Isolated. Except she was there, the two of them best friends, close as book pages. They loved each other, trusted each other. And one day that tipped into something more. Something neither one felt was wrong in the moment. "We were just sitting there, and it was like, 'Do you want to?'" he says. There was no discussion. "We did it. And it was like, 'OK, what's next?' We never talked about it after that."
Both say it happened only once more. The two never kissed. Never shared true intimacy. Just spontaneous, ill-conceived connections. Needs met when few others were.
A few months after they first had sex, Washington's sister went out one night to meet somebody. Her boyfriend, she says. Johns, the police suspected. Soon after, Washington's phone rang. His sister had been picked up by the cops. He needed to come get her, and he needed to come right away. "All I knew was my sister was in trouble," he says. "So when I showed up, and they asked me about the two of us, I said yes. I didn't know it was illegal."

http://sports.espn.go.com/nfl/news/story?id=5497517

On May 9, 2003, Washington pleaded guilty to having consensual sex with his biological sister, Caylen. He was 16, she was 15.
"Incest," he says, looking straight ahead.
He says he didn't plan to do it. He was a teenager. Unstrung. Unsupervised. His world was at war. He was scared. Isolated. Except she was there, the two of them best friends, close as book pages. They loved each other, trusted each other. And one day that tipped into something more. Something neither one felt was wrong in the moment. "We were just sitting there, and it was like, 'Do you want to?'" he says. There was no discussion. "We did it. And it was like, 'OK, what's next?' We never talked about it after that."
Both say it happened only once more. The two never kissed. Never shared true intimacy. Just spontaneous, ill-conceived connections. Needs met when few others were.
A few months after they first had sex, Washington's sister went out one night to meet somebody. Her boyfriend, she says. Johns, the police suspected. Soon after, Washington's phone rang. His sister had been picked up by the cops. He needed to come get her, and he needed to come right away. "All I knew was my sister was in trouble," he says. "So when I showed up, and they asked me about the two of us, I said yes. I didn't know it was illegal."