Blood Relations
Blood relation questions are easy to get right and easy to rush. The candidates who lose marks here are the ones who reason in sentences instead of drawing. A three-line diagram removes almost all the difficulty.
Updated 19 September 2026 · Almost always present, usually 2-3 questions including a coded set.
How to think about blood relations
Draw, never reason in your head
Use a fixed notation and stick to it: a horizontal line for spouses or siblings, a vertical line downward for parent-to-child. Mark males with + and females with −. Two lines of drawing beat a paragraph of reasoning, and the diagram is re-checkable when you are unsure.
Work backwards from the speaker
In "pointing to a photograph" questions, start from the person speaking and move outward one relation at a time, in the exact order the sentence gives them. Read the sentence right-to-left: "my father's brother's son" resolves as father → his brother → that brother's son.
Do not assume gender
Names and roles like "cousin", "spouse" or "in-law" do not fix gender. Many questions are unsolvable precisely because gender was never stated, and "cannot be determined" is then the correct answer. Check what the question actually told you before eliminating it.
Coded relations use symbols for relationships
A second family of questions replaces words with symbols: A + B might mean "A is the father of B". Decode one symbol at a time, left to right, building the same diagram. The symbols change between questions, so never carry an earlier meaning over.
Formulas and shortcuts
- Father's or mother's son
Brother (or the person themselves) - Father's or mother's daughter
Sister (or the person themselves) - Father's brother
Uncle (paternal) - Mother's brother
Maternal uncle - Father's sister
Aunt (paternal) - Son's or daughter's son
Grandson - Brother's or sister's son
Nephew - Husband's or wife's father
Father-in-law - Father's brother's son
Cousin
Solved examples
Q1. Pointing to a photograph, a man said, "She is the daughter of my grandfather's only son." How is the woman related to him?
- Start at the speaker and resolve the phrase from the inside out.
- His grandfather's only son must be his own father — if there were another son, the word 'only' would be false.
- So the woman is the daughter of his father.
- The daughter of his own father is his sister.
Answer: She is his sister
Q2. A is the brother of B. B is the sister of C. C is the father of D. How is A related to D?
- Draw it. A and B are siblings. B and C are siblings, so A, B and C are all siblings.
- C is the father of D, so D is one generation below.
- A is therefore a sibling of D's father — that is D's uncle.
- A is called "brother of B", which fixes A as male.
Answer: A is D's uncle
Q3. If P + Q means P is the father of Q, and P − Q means P is the sister of Q, then what does A + B − C mean?
- Decode strictly left to right, one symbol at a time.
- A + B: A is the father of B
- B − C: B is the sister of C
- So A is the father of B, and B is C's sister. B and C share the same father.
- Therefore A is also the father of C.
Answer: A is the father of C
Note the symbol '−' also tells you B is female, but the question asks about A and C, so that detail is not needed.
Practice questions with answers
1. Pointing to a man, a woman said, "His mother is the only daughter of my mother." How is the woman related to the man?
Answer: B. Mother — The only daughter of the woman's mother is the woman herself. So the man's mother is the woman — she is his mother.
2. A is the son of B. C is the mother of B. How is C related to A?
Answer: C. Grandmother — C is B's mother and B is A's parent, so C is one generation above B — A's grandmother.
3. X is Y's brother. Z is Y's father. How is X related to Z?
Answer: A. Son — X and Y are siblings, so they share a father. Z is that father, making X his son ("brother" fixes X as male).
4. Introducing a boy, a girl said, "He is the son of the daughter of my father's wife." How is the boy related to the girl?
Answer: B. Nephew — Her father's wife is her mother; that mother's daughter is the girl herself or her sister. The boy is that daughter's son, so he is her nephew.
5. If A − B means A is the mother of B, and A × B means A is the brother of B, then in M − N × O, how is M related to O?
Answer: B. Mother — M − N: M is the mother of N. N × O: N is the brother of O, so N and O share a mother. That mother is M, so M is the mother of O.
6. P is Q's daughter. R is P's cousin. What is R's gender?
Answer: C. Cannot be determined — "Cousin" carries no gender in these questions, and nothing else in the statement fixes it. This is a case where the answer really is that it cannot be determined.
Where marks get lost
- Reasoning in sentences rather than drawing the tree.
- Assuming a gender the question never stated — "cousin" and "spouse" are gender-neutral here.
- Carrying a symbol definition over from a previous question; they are redefined each time.
- Reading a compound phrase left to right instead of resolving it from the speaker outward.
Reading is not practising.
Run a timed set on blood relations and see which step you actually lose time on. Free, no card needed.
Start a timed set