Blood Relations

Blood Relations

Overview

Blood Relations is a core reasoning topic that tests your ability to decode family relationships from given statements. Questions typically present a chain of relationships (e.g., "A is the son of B, B is the sister of C") and ask you to identify the relationship between two specific people.

Success in blood relation problems requires two skills: knowing the standard relationship terms (who is a maternal uncle versus a paternal uncle) and systematically drawing family trees. Many students lose marks not because the logic is hard, but because they misread a single relationship term or draw the tree incorrectly. Master the terminology first, then practice building quick diagrams.

Key Concepts

• Generations move vertically: Parents and grandparents are above you; children and grandchildren are below. Siblings, cousins, and spouses are on the same horizontal level.
• Paternal vs Maternal distinction: Paternal relations come from father's side (father's brother = paternal uncle). Maternal relations come from mother's side (mother's brother = maternal uncle/mama).
• Gender indicators in statements: Words like son, brother, father, uncle, nephew indicate male. Words like daughter, sister, mother, aunt, niece indicate female. "Child," "sibling," "cousin," and "spouse" are gender-neutral.
• In-law relationships form through marriage: Father-in-law is spouse's father. Son-in-law is daughter's husband. Sister-in-law can be brother's wife or spouse's sister.
• "Only" is a critical word: "A is the only son of B" means B has no other sons (but may have daughters). "A is the only child of B" means B has exactly one child.
• Coded blood relations: Some questions replace names with symbols (+, −, ×, ÷) representing relationships. Decode the symbols first, then solve normally.
• Draw the tree, don't solve mentally: Even simple-looking problems become error-prone without a diagram. Always sketch.

Key Facts / Relationship Chart

Remember: Cousin is always gender-neutral in English. "He is my cousin" does not tell you whether the cousin is male or female.

Worked Examples

Example 1: Direct Chain

Question: Pointing to a man, Rekha said, "His mother is the only daughter of my mother." How is Rekha related to the man?

Solution:

• Only daughter of Rekha's mother = Rekha herself (since she's the only daughter)
• That person (Rekha) is the mother of the man
• Therefore, Rekha is the Mother of the man

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Example 2: Building a Family Tree

Question: A is the son of B. C is the daughter of B. D is the brother of B. How is C related to D?

Solution: Draw the tree:

      D ——— B
            |
        ---------
        |       |
        A       C
      (son)  (daughter)

• D is B's brother, so D is the uncle of B's children
• C is B's daughter
• Therefore, C is the Niece of D

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Example 3: Coded Blood Relation

Question: If A + B means A is the father of B, A − B means A is the wife of B, A × B means A is the brother of B, then what does P + Q − R mean?

Solution:

• P + Q → P is the father of Q
• Q − R → Q is the wife of R

Draw: P is Q's father. Q is married to R.

• So R is P's son-in-law
• P is R's Father-in-law

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Example 4: Statement with "Only"

Question: Pointing to a photograph, Arun said, "She is the daughter of my grandfather's only son." How is Arun related to the girl in the photograph?

Solution:

• Grandfather's only son = Arun's father (only one son exists)
• Daughter of Arun's father = Arun's sister
• The girl is Arun's Sister
• Arun is the Brother of the girl

Common Mistakes

• Ignoring "only" in statements → Students assume multiple children exist when "only son/daughter" clearly limits to one. Read the word "only" as a strict constraint.
• Confusing paternal and maternal uncles → Father's brother and mother's brother are both called "uncle" in English, but in Indian language contexts (or detailed questions), they differ. Note which side of the family is referenced.
• Assuming gender from names → A name like "Kiran" or "Suman" is unisex. Never assume gender unless the statement explicitly says "he/she" or uses gendered relationship terms.
• Reversing the relationship direction → "A is the father of B" means A→B (A is senior). When asked "How is B related to A?", the answer is son/daughter, not father. Always check which direction the question asks.
• Not drawing a tree for chains of 3+ relationships → Mental solving works for 2-step problems but fails for longer chains. Spend 10 seconds drawing a small diagram to avoid silly errors.
• Forgetting in-law creates a link, not blood → Spouse is not a blood relative. Father-in-law is through marriage. Be careful when the question specifically asks about blood relations.

Quick Reference

• Same generation: siblings, cousins, spouses, siblings-in-law
• One generation above: parents, uncles, aunts, in-laws (spouse's parents)
• One generation below: children, nephews, nieces
• "Only son/daughter of my parents" = myself
• Grandfather's only son = my father (if I exist)
• When stuck: draw males with a square, females with a circle, use horizontal lines for same generation, vertical lines for parent-child