Amusing, Or Disturbing...

I am 56 now but this happened I guess around 1993 when I was in my upper 20's. We (me and wife) moved into an apartment complex near where we grew up. A young girl was always hanging around the complex. Sometimes see her with another girl who later found out was her older sister. Anyway she started talking to us and eventually kind of invited herself to hang out with us in the evenings. She was 17 at the time but turned 18 very shortly after that.
I had 3 golfing and poker buddies that were always coming by. Same age as me. The girl was tall, like 5-9, skinny no major tits or ass but she was very pretty. And yes me and my buddies noticed.
One day she came by when it was just me and one of my friends. The talk got a little sexual and SHE TOOK THE LEAD. Basically she offered to fuck, BOTH OF US! And yes we tag teamed her. From there me, him and our other 2 buddies started having sex with her on a regular basis. Sometimes group sex. 3sums, 4sums, 5sums. One great night we put her in a bedroom and the 4 of us pulled a train on her all evening. One guy would come out of the bedroom and yell "next".
But... Now the funny part. Our fun lasted about a year. One thing we all noticed about her was that she HATED to suck dick. Getting her to give head was nearly impossible. Luckily we were all 20's horny guys and a naked 18 year old was all we needed for a hard on.

Now the funny part. Fast forward 20 years. Another friend of mine dated her older sister for a few months. Talking we made the connection between the sisters. We talked about the sex I had back in the day with baby sister. He told me about older sister. Both girls hated to suck dick! Well he actually asked the older sister and she told him that giving head brings back bad memories. Because their DADDY (real dad) used to make them give him blowjobs!!!
I knew who her dad was, he was my school bus driver all through high school.