Family Tree Puzzles

• How to handle several facts at once about a bigger family (3 generations, multiple siblings and cousins).
• Recognising cousin relationships (same grandparent, different parents) and uncle/aunt relationships.
• A systematic way to build the whole tree first, then answer any question about it without redoing the work.

1. Build the full tree before answering — list every stated fact as a branch, generation by generation.
2. Cousins share a grandparent but have different parents.
3. Uncle/aunt is your parent's sibling; nephew/niece is your sibling's child.
4. Great-grandparent/great-grandchild span three generations.

"A is the father of B and C. B is the father of D. C is the mother of E." How is D related to E?

Step 1 — tree: A -> B -> D  and  A -> C -> E
Step 2 — B and C are siblings (both children of A)
Step 3 — D and E are children of siblings, i.e., same grandparent A, different parents
Answer: D and E are cousins.

• Forgetting to check whether two people share a grandparent (cousin) versus a parent (sibling).
• Getting confused with too many names — always label the tree by generation as you read each fact.
• Answering "brother/sister" for people who are actually cousins (they don't share the same parents).

• If X and Y are children of two brothers, how are X and Y related?
• If P is the sibling of Q, and Q is the parent of R, how is P related to R?
• Build a 3-generation tree from: "A is father of B. A is father of C. B is father of D."

Open the Practice tab for graded questions on Family Tree Puzzles.