Got my sister pregnant

It wasn't planned; we hadn't gone out together, but met up later by accident. My sister's boyfriend had dumped her, and she was drinking heavily. I had gone to a movie alone and decided to have a drink before heading home. I came across my sister drinking at the place I entered to get my drink. Seeing her drunk, I decided to take her home with me. On arriving home, she said she was horny and asked me to fuck her. I said I didn't have condoms; no need for them, she responded. I'm on protection, so I decided to fuck her, which I did twice, once before she fell asleep and again in the morning. It was several hours later that she noticed an unread text message. Her booster shot was overdue, and she wasn't as protected as she thought she was. Turned out she wasn't protected at all; she got pregnant, and she decided to have the baby. Our daughter was born yesterday, healthy, with no problems at all. Our mother is very happy to be a grandmother; less so about how it happened. Our father left us all years ago and hasn't kept in touch.