I [29M] Cheated on my Girlfriend [27F] With Her Older Sister [31F] [MF]

I’ve been dating my girlfriend for 3 years and we’ve had overall a very good relationship together and everything’s been solid. I also have a great relationship with her family, and I see them all the time since she still lives at home. Her sister also lives at home, and I’m not going to lie, I’ve always been very attracted to her.

She looks like my gf, but with more curvier features like a bigger ass and hips. I’ve also always gotten along really well with her, we seem to have similar interests and have great conversations about various topics. I’ve fantasized about her often but never thought anything would actually happen.

We’ve flirted a bit here and there and she tends to be a little handsy (nothing sexual, just putting her hand on my shoulder or back sometimes). However, nothing remotely close to crossing the line.

That all changed quickly this past weekend. On Saturday I went over to her parents house in the morning as I told her mom I’d help her haul some tree debris to the front. It didn’t take too long, and I went back inside to relax. My gf and her mom told me they were going to go shopping for a bit and that there was coffee boiling and some leftovers in the oven she had ready for me, so I should stay and relax until they’re back.