Takes two Individual records as parameters and returns TRUE if they share their Y chromosome. Only males have a Y chromosome, so this function will always return FALSE if either of the two people are female. Males inherit their Y chromosome from their fathers. This means that a man will have not only the same Y chromosome as their father, but also as their father's father, and his father, and so on. It will also mean that they have the same Y chromosome as the sons of all of those people (and their sons etc.), and that they have the same Y chromosome as their own sons, and their sons (and their sons etc.).
A reference to an Individual record..