prolog code required!

I do not need your explanation of family tree.

I asked many times ppl explain to me what cousin is.

I need prolog code.

here is the question:

Define a rule for checking if X and Y are cousins of the same generation, i.e., X and Y are descendents of a common person and both are same no. of links down from the common ancestor.

Suppose the double arrows depict the relationship married. Two indi- viduals are also married if they have a common offspring. Rewrite the rules grnephew and niece taking into account relationships by marriage also.