Paying the Debt

Long story short. I'm Kate 25 and just got into university and just finished my courses. I've never was good at studying and preferred to party. I barely got in to university and was told by my parents I would be cut off financially if I didn't pass my courses. Luckily I had a nerdy brother Peter 27 who only studied and always did great. So as I was just passing each year until my final year and everything was getting harder, I asked Peter for help. He agreed to help me and the only problem was me finding time to study with him as I still liked to party. But then it became quite clear even to me I would fail if I didn't start to study. But Peter had become less willing to help as I hadn't been attending the study sessions before. I had a hard time getting him to to help me and so I offered him something he hadn't had before SEX. Telling him if he helped me I would give him sex for 2 weeks after I passed. He was uncertain and said was wrong, but I said I had been having regular sex for years and was on the pill and it would just sex. After a while he agreed on the condition I turned up for every study session, miss one and he wouldn't help anymore. It was hard making each session and I was late a couple of times, but then the exams and I passed in the middle of class. Not as a honor student like Peter had. But it was a pass and my parents were proud of my passing higher than they thought I would get. So after weeks of partying after finishing university, I finally remembered my deal with Peter. Peter hadn't said anything and was going along as was usual for him. But I had promise 2 weeks of sex with Peter and I intended to keep that promise. But I couldn't just make 2 weeks available while in the city, as the urge to party would take over. Then Peter was going to our family cabin for some peace and quiet away from the city, he painted landscapes in his spare time and I think he's really good at it. So I said would join him as well, this was a shock to my parents. Who thought I didn't like the quiet of the mountains, I told them I was a little burnt out after years of university and recent partying. I' told Peter I was going to pay my debt to him and I don't he knew what I was talking about and on remembering he got a shocked look on his face. On arrival at the cabin it was as isolated as I remembered and after we had unpacked the car I led Peter to a bed and started to undress him, he was a little awkward and I had to show him everything he needed to do except get a hard-on. I was surprised by the size of his cock, it was bigger than most I've seen. After the first fuck he learnt quickly and was soon fucking better than most of my lovers before. I was really happy that he learnt so well and after 2 weeks and our return to the city I missed him fucking me. I took him out several times after our return home and introduced him to Maureen 25 and she got him into bed and became his girlfriend soon after. I was a little jealous of Maureen, but we had also been lovers and had slept together a few times. So I again went with Peter to the cabin and Maureen also joined us. I made sure it was the 3 of us in the same bed each night and got my fair share of Peter's cock. Peter is thinking of asking Maureen to marry him, but isn't sure she will answer Yes. I think she will agree to marry him, so I'm sneaking into his bed at night and getting as much sex as I can now, just in case. I'm a bit surprised that Peter hasn't become more of a party guy and only goes out with me or Maureen and we have to ask him. Maureen is sleeping over more and more now and it's becoming hard to get Peter to myself.