Nearly caught out

I used to call on some friends on my way home, quite often one of their daughters was there, after a while we started fucking , her parents knew about it and didn't mind , she enjoyed being fucked , not getting much at home. I knew she had a sister. One time i called in as I often did , she seemed a bit off with me not her usual chatty self, a bit strange I thought ,I was just about to put my hand up her skirt and rub her pussy, I had a shock when she walked in the room , it was her identical twin i was talking to who knew nothing about me fucking her sister. That was about 2 seconds from a major disaster as she was 100% straight no nonsense no playing away women .I just managed to pass it off by talking to her parents as i would had i been alone with them. I never told my fuckbuddy how close it had been.