Is it normal that i still get horny thinking about my dad seducing my wife

When I was courting my future wife, my mum was ill in hospital and my gf and I were in my parents bedroom. We just had bathrobes on and had the lights off because we were watching a guy in an alley way with a youngish girl. It was obvious they were doing stuff but hard to really see exactly what, but it was making us both horny. My gf stood in front of me and I played with her tits while she fondled my cock. My dad had come home from the hospital and walked in on us, he went a bit ape and told me to go to my room and asked my gf what her father would say if he knew what we were doing. I pleaded with him not to call her dad and he told me to go to my room. I left and I was really panicking that her dad would flip. I lay there for ages wondering what would happen and eventually she came into the room and said everything was cool. She told me my dad had asked her what we were doing and she explained about the couple in the alley. My dad knew the guy and said that the girl was just too horny. He stood behind her as I had done and she felt his cock pressing against her robe, he put his arms around her and slipped his hands inside to feel her tits pulling the robe back he let it slip to the floor so she was naked. He put the light on and pressed up hard behind her and he fingered her puss. She said she was scared, because of the threat of telling her dad, but later admitted she was really horny. She started to come and she noticed that the guy in the alley appeared to be doing the same but was watching the window at the same time. My dad blew his load all over her back and then gave her some tissues to get cleaned up. He told her he wouldn't call her dad but that he would like to carry on what they had started another time, then said she'd better go to find me. Later she continued seeing my dad and fucking with him and also occasionally his friends. I knew about it and continued to fuck her whenever we were together, even if my dad had been there earlier. I never confronted my dad and I can't say I was unhappy with the situation as we got married after a couple of years and he was still seeing her and fucking her about as often as I was. Is it normal that I wasn't upset or angry, even when he had threesomes with his mates with my wife? Sorry I know it's a long story but I couldn't find a way to shorten it.