Blood Relations — Shortcuts, Tricks, and Solved Examples | TNPSC, SSC, Placement

Quick Concept Summary

Blood relations problems test your ability to trace family connections through chains of relationships. There are three main types:

1. Direct questions — "How is X related to Y?" 2. Coded relations — "A says to B: your mother is the wife of my father's son" 3. Puzzle type — A paragraph describing multiple people, then 2–4 questions

Key strategy: Always draw a family tree. Never try to solve in your head for multi-step problems.

Family Relationship Quick Reference

Parent-Child Relations

Sibling Relations

Extended Family

Family Tree Symbols

Worked Examples

Example 1 — Direct (Easy)

Q: A is the father of B. B is the sister of C. D is the husband of A. How is C related to D?

• A is B's father → A is male
• D is the husband of A → D is female and A is married to D (D = mother)
• So D is the mother of B and C
• C is D's child

C is the son or daughter of D. Since we don't know C's gender: C is the child of D.

Example 2 — Multi-step

Q: Pointing to a boy, Sunita said, "He is the son of my grandfather's only son." How is the boy related to Sunita?

• Sunita's grandfather's only son = Sunita's father (grandfather has only one son)
• The boy is the son of Sunita's father → boy is Sunita's brother

Example 3 — Coded Relation

Q: A says to B: "Your mother is the wife of my father's only son." How is A related to B?

• A's father's only son = A himself (only son)
• So: B's mother is the wife of A
• That means B's mother is A's wife
• Therefore A is B's father

Example 4 — Coded Relation (Trickier)

Q: Introducing a man, a woman said, "He is the only son of the father of my mother." How is the man related to the woman?

• "Father of my mother" = woman's maternal grandfather
• "Only son of maternal grandfather" = woman's mother's only brother = woman's maternal uncle

The man is the woman's uncle.

Example 5 — Puzzle (Paragraph Type)

Q: Read the following and answer the questions:

"P and Q are siblings. R is the father of P. S is the husband of T who is the mother of Q. U is the daughter of S. R has no daughters."

1. How is T related to P? 2. How is U related to Q?

Step 1: Draw the tree.

• R is the father of P. R has no daughters → P is a son.
• P and Q are siblings → Q is also R's child. Since R has no daughters, Q is a son too.
• S is the husband of T. T is the mother of Q → T and S are Q's parents.
• But R is P's father and P & Q are siblings → R = S (the same person) OR T is R's wife.

Most logical reading: S = R (same person with different names? No). Actually:

• T is Q's mother, so T is also P's mother (since P and Q are siblings)
• R is P's father → R and T are married

So R = S? The problem says "S is the husband of T" — if R is the father, R must be the husband of T. So S = R (or there's a step-family). For exam purposes: T is P and Q's mother, R is their father.

• U is the daughter of S (=R and T) → U is P and Q's sister.

Example 6 — Mixed Gender Inference

Q: Introducing a photo, Ravi said: "She is the wife of the only son of my grandfather." Who is the person in the photo?

• Ravi's grandfather's only son = Ravi's father
• Wife of Ravi's father = Ravi's mother

Example 7 — Three Generations

Q: A is B's son. B is C's father. D is C's brother. How is A related to D?

• A is B's son → A is B's child (one generation below B)
• B is C's father → C is B's child (same generation as A)
• D is C's brother → D is also B's child (same generation as A and C)

A and D are both children of B. A is D's brother (or sibling).

Example 8 — Pointing/Photo Question

Q: Looking at a portrait, Deepa said, "His mother is the wife of my father's son. I have no sibling." Whose portrait is it?

• "I have no sibling" → Deepa's father has only one son = Deepa herself? No — Deepa is female.

Wait: "my father's son" — Deepa's father's son = Deepa's brother. But she has no sibling. So "my father's son" = Deepa's father himself? No.

If Deepa is female and has no siblings, then her father has no sons. "My father's son" — if there's no son, this statement can't be true unless it refers to Deepa's father himself through marriage.

Actually: re-read — "wife of my father's son." If Deepa has no sibling, "father's son" refers to Deepa... but Deepa is female. This is a trick: it must mean the person IS Deepa's father's son = Deepa's non-existent brother.

Standard interpretation for this classic puzzle: "My father's son" = the speaker (when male) or the speaker's brother. Since Deepa is female and has no sibling, this refers to Deepa's husband (common exam interpretation where "father's son" still refers to the reference person through marriage context).

Alternatively, the standard version of this puzzle: "His mother is the wife of my father's son. I have no sibling." Since Deepa has no sibling, "my father's son" = Deepa (if Deepa were male) — but Deepa is female. So this is actually impossible OR "father's son" = Deepa herself in a loose sense, meaning the wife is Deepa. So: his mother is Deepa → the portrait is of Deepa's son.

Shortcuts and Tricks

Trick 1 — Always draw the family tree

For any problem with 3+ people, draw before solving. Attempting these mentally leads to errors.

Trick 2 — Work right to left for chained descriptions

"A is the son of B's mother's brother's daughter" → Start from the end: daughter of B's mother's brother → B's mother's brother = B's maternal uncle → Daughter of uncle = B's cousin (female) → A is the son of B's female cousin

Trick 3 — Gender words are clues

Male indicators: son, brother, father, uncle, nephew, grandfather, husband Female indicators: daughter, sister, mother, aunt, niece, grandmother, wife

Trick 4 — "Only son/child" eliminates options

"Only son" means no brothers. "Only child" means no siblings. Use this to lock the family tree.

Trick 5 — "Myself" trick in coded relations

"My father's only son" = myself (if the speaker is the only son) "My mother's only daughter" = myself (if the speaker is the only daughter)

Exam Pattern

TNPSC Mental Ability: 3–5 questions per paper. Usually 2–3 direct/coded questions and 1 small puzzle. Difficulty is moderate.

Bank PO / SSC: 5-question puzzle sets with 4–6 family members are common, especially in Bank PO (Seating + Blood Relations combo).

Placements: 2–3 questions. Usually a paragraph with 4–5 people, then questions about specific relationships.

Practice Questions