I was adopted by my parents at age two. My first memory of incest was when I was in preschool and as my mother drove me home, she fondled my crotch as she drove. Sometimes she would come to bed with me and fondle me there. Full intercourse started when I was eight and continued for seven more years.
It also included my sister who was four years older and also adopted. Soon I was having intercourse with her and this lasted for ten years, even after she was married. My sister and I still get together about four times a year and enjoy each other very much.
I am now 41 and she is 45. The experiences were very positive, both my mother and sister were gentle and kind.
I always received positive reinforcement when I pleased them. To say the least, I was trained very well in pleasing a woman, and my wife can attest to that.
I cannot think of any negative results other than it took me 18 years after I was married to tell my wife and I always felt guilty of holding back with her. We fantasize regularly now.