Broken Prophylactic

I started fucking my sister Deborah after return from service in the army. Deborah was lonely parting with her then boyfriend and I was horny. We were drinking and ended up in bed fucking. I had army issued condoms, prophylactics my sergeant called them and as I had a few we continued using them. But one broke and I blew my whole load of sperm into Deborah, not worried we left it till morning to clean ourselves up. Now 4 months later Deborah is pregnant. So we don't need condoms and still fuck, tests show the baby is healthy and we're happy with that.