It started as a joke a few years ago, me and my sister tried sex and we enjoyed it and until a few months ago I liked it but now I've met a girl and I think I'm in love and I don't know how to tell it to my sister. Once I've tried to asked her hypothetically if I met another girl and I wanted to end our relation. She almost killed me and said she would tell every one about us and she has proves as you can see.