I had the experience with my dad when we were left alone after my Mom died.
Sorry for you mom, #1
I had sex with my own dad after few years when he had suggested could we do it.
I was married to my first husband then and wasn't used to such a thought when dad first introduced such a chance. It took years before we did it.
Dad didn't exactly suggested it to me, but he was giving lots of hints and making wishes how he hoped one day he could have sex. But you could read between the lines, he meant me. He was just too shy to admit it out loud.
We talked about it for years, going through every little detail. I had tried to help and encourage him to meet women, but I admit I felt horny when I began to suspect he was meaning me.
After I divorced and after I had got my own life back in rails, I was getting used to the thought and thought it a lot. Finally we did it. Despite his countless wishes and hints, and all the hot talking we had before, it was I who had to ask would he like to make love with me.
I wish I would had understood him and agreed to do it earlier, because like you said, feeling your own father inside you, cuming inside you, knowing all the risks it involves and knowing he made me, is amazing!
I used to pass dad's bedroom in the A.M. after mom went on her early shift at the hospital and would see dad's big, hard wood standing out of his pj bottoms while he slept on his back. Finally, I could not stand it any longer and mounted him for a ride. When he woke up in seconds, he was at first shocked then we began our secret life, fucking like mad.