Not so Virgin Sister

My sister the perfect bride married into a wealthy family last month. On getting engaged she had to prove she was a virgin and was examined by a doctor for the grooms family. Which she passed as she was at the time a vaginal virgin. Her vagina had never been fucked, but her ass I've been using regularly for over a year. Her vagina is the only hole I hadn't cum in and it wasn't because I couldn't have fucked there. But we didn't condoms or a reliable form of contraceptive. Not willing to risk making a baby we kept to her mouth and ass. Now married and poked by her older overweight husband, I'm free to fuck her pussy. With a forty year age gap and his continuing ill health, I might as well use her and I've also got married myself last year and my wife is pregnant and so fucking my sister is my usual sexual partner at the present. My new brother in law has me and my wife living with him and my sister as company for her while he works his business.