Sister In Law Sex

When I was 12 my parents went on a special 6 week vacation to Australia visiting friends I was staying with my elder brother and sister in law who was 19 at the time, to cut a long story short she caught me wanking with her knickers and first of all went mad at me then seeing my distress gave me a cuddle we then both got carried away and I kept on trying to go further and further starting with kissing then feeling her bottom then breasts then between her legs finally getting her knickers off and fucking her bare back didn’t even think of birth control it was just the most fantastic feeling cumming inside her, after she said it must not happen again but I blackmailed her and I think she wanted to as well but couldn’t admit to cheating on my brother with his underage brother also the law but we had sex many times over that time and I didn’t realise it at the time but there’s a good chance I got her pregnant and my niece is actually my daughter,