When I was 20 and my mother divorced my father for his infidelity, being the oldest of my siblings I filled my father's shoes. My mother and I became very dependent on each other, and one day when she had a nervous breakdown she offered herself to me as long as I never told anyone, and made sure my siblings didn't find out.
It wasn't a romantic relationship or anything, it was more like a friends with benefits thing. My mother assured me she couldn't get pregnant, and after a few months she ended up pregnant with our son.
To cover her tracks, my mother had a fling with a guy in her college class, and blamed him for the pregnancy. After that we stopped having sex, and our son was born, my mother begged me to keep our son's origins a secret, and I have my whole life.
My step-brother has no idea he is my son, and he is in his 20's now. I think it's better he never knows he is the product of i****t as it will stigmatize him his whole life.