I got a surprise on my return

I was 29, work on contracts and didn't have girlfriend and worked away quite a bit. I returned home after one contract was finished and my younger sister was 23, like me had no one special. We lived with our mother then 46 divorced, so we were together most of the time and it started snowing hard and so nobody wanted to go out anywhere. Mucking about with my sister ended up in us having intercourse and getting caught by our mother. Shocked at first, she soon recovered and asked to join us and so we all had sex together. Two weeks later I'd a new contact and went away for 6 months and on my return, I found I'd gotten my sister pregnant; we hadn't been as careful as we first thought we had. Family beliefs meant my sister would've the baby who was healthy, which is because we're half siblings. My father died in a car accident and my mother married again afterwards and when my sister was 15 her new husband left us. I've a different surname and so I married my sister, and we all moved to another state and now had 4 children together in the following 9 years. No problems with any of them.