Anybody know prolog ?

Hi to all.

I've to find an assignment to study my final exam. It's about prolog programming and relationships. For example :

X is father, Y is mother. If A and B is a child of X and Y, they're brother. Another example; if C is A's grandfather, and D is B's grandmother, X and Y is married. Hmm also, if E is X's brother, E is A and B's uncle.

It's a complicated coding. I found a full source code about that problem. But I've lost right now

So, can I find any example that similar to what I want ? Also, where can I find understandable prolog source codes to study ?

Thanks a lot for the replies