He says he's fucking his sister for more than a year and things started to get a bit bored. The good part is that she thought the same. She has a girl friend with who she likes to hang out and they are always together. He suggested to his sister if she would like to join them in a threesome. It took awhile but the other day his sister called him very excited saying her friend agreed. He says it was not bad for a first time threesome.