If someone X is a relative of someone Y then Y is a relative of X.
If someone X is a child of someone Y then Y is a parent of X.
If someone X is a parent of someone Y then Y is a child of X.
If someone X is a parent of someone Y then X is a relative of Y.
If someone X is a male child of someone Y then X is a son of Y.
If someone X is a female child of someone Y then X is a daughter of Y.
If someone X is a male parent of someone Y then X is the father of Y.
If someone X is a female parent of someone Y then X is the mother of Y.
John is male.
Mary is female.
Bill is male.
Tom is male.
Bob is male.
Sue is female.
John is a child of Mary.
Bill is a parent of John.
Sue is a child of Tom.
Bob is a parent of Mary.