Can one USER parent another USER

I’m passing along a CD of music, almost like a chain letter (but not annoying) and I wan’t to use the wordpress site to cultivate a community around listening to the music, but one of the things I also want to do is make it track who passed to who. And I wanted to use the Parent Child function, so that if Joe passed it to John, the Joe is a user would be a parent to John, and John would be a parent to whomever he passed it to. Is this possible? Or any other ideas?