I need help with how to organize/ track webiste members?

[jjblond]

I am new to affiliate programs and am trying to make my own website. I bought SBI and have been pretty happy with it, but I am not sure it can accomplish what I am trying to do. I am looking to make a website and the website would have groups of people interested in different things.
Example:

1. motorcycles
* joe
* bob
* sue
2. trucks
* sally
* john
* mark
3. cars
* John
* lisa

I need to know John is in the cars group and not the trucks group. Each group can have their own log-in and then each person can log-in under the group.

What do I need to do to accomplish this?