A is the son of C; C and Q are sisters; Z is the mother of Q and P is the son…

In family-tree blood-relation puzzles, first convert every clue into a parent-child or sibling link, then move up or down the generations one relation at a time. Two people described as sisters share the same parents; a parent's sibling is that parent's child's uncle (if male) or aunt (if female), and is called maternal or paternal depending on whether that sibling belongs to the mother's side or the father's side.

1. C and Q are stated to be sisters, so they share the same mother; since Z is given as the mother of Q, Z is also the mother of C.

2. A is the son of C, so C is A's mother, making Z - C's mother - the maternal grandmother of A.

3. P is the son of Z, so P is a sibling of C and Q, Z's other children.

4. Since P is Z's son and C is A's mother, P is C's brother, which makes P the maternal uncle of A.

• The claim that P and A are cousins is inconsistent with the family tree: P sits in the same generation as C and Q, one level above A, because P and C share the same parent, Z; cousins would instead be two people whose parents are themselves siblings.

• The claim that Q is the maternal grandfather of A cannot hold: Q is explicitly one of the two sisters, so Q is female and belongs to A's parent's generation, not a grandparent generation, and cannot be labelled grandfather.

• The claim that C and P are sisters is inconsistent with gender: P is introduced as the son of Z, that is, male, so the sibling relationship between C and P is a brother-sister pair, not two sisters.