Sleepover Mistake Turned Sister Into Sex Machine

My sister is four years younger and at the time I was just 17. And I was the first bf her friend ever had. So the first time her friend stayed overnight I slipped into bed with the two of them and ended up screwing my new gf with my sister sleeping next to us. Later that night I woke up hard and horny for more pussy. It was different but I was to into it to realize I was mistakenly fucking my sister instead. She was much more active, relaxed, and into it. Was it because she was asleep or just that much more excited. So much better I thought and this was only my third fuck ever. Obviously my sister thought it was good enough that started fucking at least once a day. Me and my sister fucking was all I lived for at the time. And I loved that I was seeing her up close and personal as she developed into such a hot foxy girl. My sister got better looking and more sexual over the next 7 years or so. And she continues to get better in all ways. She let me do whatever I wanted and encouraged experimenting. We were sneaking but at some my parent had to suspect something or they were just that mindless. Our sex continued until 22 I got a decent job and moved out. My sister visited regularly and often slept over. Then I met a girl who got too suspicious. So I grew up and chilled my sister by cutting her off sexually. We still talk but no more sex except twice or maybe three times. I am 24 now and still think of my sister when I masturbate. So pretty with the best ass tits and tight pussy that she knows how to move. She has the best rythm and that is one thing she taught me. Still my sister is the best fuck I have ever had. I am so grateful for my mistake that night.