Lazy Student

My sister has always been a very lazy student, but just scraping by was cutting it at university. With our parents paying for everything, they wanted her to do well and started saying they would cut her off if she didn't improve. Desperate she turned to me, her only brother and a nerd according to her. I wasn't as dependent on our parents as she was, I had gotten a scholarship and was pretty well set, with tutoring adding to my income. But tutoring wasn't going to help my sister, as she had never gotten into a study routine and with a routine, well you don't do very well. But I wasn't all that interested in trying to tutor her as she wouldn't stay focused for the time needed. But the treat of no money from our parents had raised her focus at that time, but whether it would last was another matter. Seeing I wasn't interested all that much in tutoring her, because she knew I thought it a waste of my time. She offered me sex in return for helping her, that raised my interest as I wasn't anything like a ladies' man. Fucking my sister hadn't been on my mind, but once it was I was very interested. So, I started tutoring her and she taught me to fuck her, then we had to isolate and continue our courses online. My sister and I were at our home and our parents were with our grandparents (mother) as they were old and frail. My father's parents died in 2015 and 2017, our parents relied on me to keep my sister learning. But they didn't know we were fucking our brains out as well. Her results improved and improved, and I succeeded in getting her into a study routine and that was what improved her results more than anything else. Since the lockdown finished her results have stayed higher because of her sticking to her study routine and she found she can still do everything she wants too. She also fucks me from time to time, not because it was part of our agreement, but she likes our personal time she says. I too, like the personal time with my sister and I really like fucking her. She has help me get dates and she said I'm not a big nerd anymore, just slightly nerdish.