His cousin likes to do dirty things when they are alone
The fact that she lost her virginity with him has nothing to do with it. That’s not really important to her, it’s the first time doing something she was probably going to do at any time. There are other first times and they don’t matter much either, this one doesn’t have to matter either. What is important, for him at least, is that his cousin likes to do dirty things when they are alone. And all he has to do is please her in whatever she wants. In exchange, he can fuck her pussy and she gives him as many blowjobs as she can give him. Then you can pleasure yourself while cumming anywhere on your body.