My Sister's First Boyfriend Was A Cuck

When I was 14, my 12 year old sister Mia came up to me and asked if we could fuck. I was surprised because she had a 13 year old boyfriend named Jim. We had messed around before when around a year before, but it stopped once she started dating. It turned out that Mia had told Jim about how we used to fuck every now and then, and it turned him on that his girlfriend liked her brother's cock. I was a bit shocked, but I kinda liked the idea - fucking my sister was always fun. We were home alone, so I was ready to get started. Mia and I undressed and she got on her knees and started sucking me off. Jim was on the couch, rubbing his dick. It was kinda weird at first, seeing Jim just sitting there as my sister was gobbling up my boner. It felt good, so I didn't really care. I came on her face after a few minutes, and she moved on to Jim and sucked him off. Jim was already close and he finished in Mia's mouth after less than 10 seconds. This lasted for almost a year until Mia and Jim broke up because we moved away, but Mia and I continued to fuck even still.