Vocabulary you need
- Father's or mother's father: grandfather. Father's or mother's mother: grandmother.
- Father's or mother's brother: uncle. Father's or mother's sister: aunt.
- Brother's or sister's son: nephew; daughter: niece.
- Father's or mother's sister's or brother's children: cousins.
- Spouse's brother or sister: brother-in-law or sister-in-law. A wife's father is the father-in-law.
The side of the family matters in some exams (paternal or maternal), but many questions only need the generation and gender.
A notation that works
- Use + for male and − for female.
- Join spouses with a horizontal line and siblings with a line above them.
- Place parents above children and write names or initials.
- Mark the person the question asks about with a star.
A method
- Break the statement into links.
- Draw each link on the tree starting from the most definite one.
- Determine gender where it is stated or implied.
- Find the relation between the two people the question names.
- If gender is unknown, the answer may be "cannot be determined".
Worked examples
Example 1. Pointing at a man, Rita says, "His mother is the only daughter of my mother." How is the man related to Rita? Rita's mother's only daughter is Rita herself. So the man's mother is Rita; the man is Rita's son.
Example 2. A is the brother of B. B is the sister of C. C is the father of D. How is D related to A? A and B are siblings, and B and C are siblings, so A, B and C are siblings. C is D's father, so A is D's uncle (A is male); D is A's nephew or niece (gender of D is not given).
Example 3. Introducing a woman, a man says, "She is the daughter of my father's only son." The man is his father's son, and since the father has only one son, "my father's only son" is the man himself. So the woman is the man's daughter.
Example 4 (coded relations). If "A + B" means A is the father of B, "A − B" means A is the mother of B and "A × B" means A is the brother of B, then in P + Q × R, P is the father of Q and Q is the brother of R, so P is the father of R.
Example 5. X's mother is Y's sister. How is Y related to X? Y is X's mother's sister, so Y is X's maternal aunt.
Example 6. M is the father of N. N is the sister of O. P is the mother of O. How is P related to M? P is the mother of O and N's sister is O, so P is also N's mother. M is N's father. So P and M are the parents of N and O: P is M's wife.
Common traps
- Assuming gender where it is not stated. Names such as "Sam" do not decide it.
- Skipping a generation.
- Confusing paternal and maternal sides.
- Forgetting "only" in "only daughter" or "only son".
A practice routine
- Day 1: single-link relations and vocabulary, ten questions.
- Day 2: pointing-at-a-person problems with a tree.
- Day 3: coded relations (+, −, ×).
- Day 4: a timed set of 12 at 50 seconds each.
Where it appears
Blood relations appear in banking reasoning, SSC CGL reasoning, railway reasoning and MAT papers. Related: direction sense and syllogisms.
Practice tests below are published by institutes and educators on TestMint.
