Blood Relations and Family-Tree Puzzles — RRB NTPC Study Notes

Overview

Blood relations questions test your ability to decode family relationships through verbal descriptions and logical reasoning. In RRB NTPC, expect 2–4 questions on this topic in the General Intelligence and Reasoning section. These problems appear deceptively simple but require careful attention to gender, generation gaps, and relationship chains.

The core skill is translating English relationship terms (brother, sister-in-law, maternal uncle, paternal grandmother) into a mental family tree, then answering "How is X related to Y?" Most mistakes happen when students rush through pronouns (he/she) or confuse maternal vs. paternal sides. Mastering standard relationship vocabulary and drawing quick diagrams will ensure you score full marks on these questions within 30–45 seconds each.

Family-tree puzzles extend this concept by presenting multiple clues about a larger family and asking you to determine specific relationships. Both question types reward systematic diagram-drawing over mental guesswork.

Key Concepts

• **Direct relations**: Father, mother, son, daughter, brother, sister, husband, wife. These form the foundation of all other relationships.

• **One-generation extended relations**: Uncle (father's or mother's brother), aunt (father's or mother's sister), nephew (brother's or sister's son), niece (brother's or sister's daughter). Always distinguish paternal (father's side) from maternal (mother's side).

• **Two-generation relations**: Grandfather, grandmother, grandson, granddaughter, great-grandfather, great-grandson. Count the generation jumps carefully.

• **In-law relations**: Created by marriage. Brother-in-law (spouse's brother OR sister's husband), sister-in-law (spouse's sister OR brother's wife), father-in-law, mother-in-law, son-in-law, daughter-in-law.

• **Cousin relations**: Children of your uncle or aunt are your cousins. The exam rarely goes beyond first cousins but may test whether you recognize "my father's brother's son" as "my cousin."

• **Gender sensitivity**: "Only son" means no brothers. "Only child" means no siblings at all. "Only daughter" means no sisters but may have brothers. Read carefully.

• **Chain principle**: If A is B's father and B is C's mother, then A is C's maternal grandfather. Break complex statements into step-by-step links.

• **Symmetry check**: If X is Y's brother, then Y is X's brother or sister (depending on Y's gender). Use this to verify your answer.

Formulas / Key Facts

**Standard Relationship Terms:**

1. **Paternal uncle** = Father's brother | **Paternal aunt** = Father's sister 2. **Maternal uncle** = Mother's brother | **Maternal aunt** = Mother's sister 3. **Brother-in-law** = Husband's/wife's brother OR sister's husband 4. **Sister-in-law** = Husband's/wife's sister OR brother's wife 5. **Nephew** = Brother's/sister's son | **Niece** = Brother's/sister's daughter 6. **Grandson** = Son's/daughter's son | **Granddaughter** = Son's/daughter's daughter 7. **Cousin** = Uncle's/aunt's child (son or daughter) 8. **Son-in-law** = Daughter's husband | **Daughter-in-law** = Son's wife

**Quick Gender Markers:**

• Male relations ending in -er: Father, brother, grandfather
• Female relations ending in -er: Mother, sister, grandmother, daughter
• Uncle/nephew/son are male; aunt/niece/daughter are female

Worked Examples

**Example 1:** Pointing to a man, Reena says, "He is the son of my father's only son." How is that man related to Reena?

**Solution:**

• "My father's only son" = Reena's brother (since father has only one son, and Reena is female, that son is her brother).
• "He is the son of my brother" = He is Reena's nephew.

**Answer:** Nephew

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**Example 2:** A is B's sister. C is B's mother. D is C's father. E is D's mother. How is A related to D?

**Solution:** Draw the family tree step-by-step:

• C is B's mother → C is parent, B is child
• A is B's sister → A and B are siblings, both children of C
• D is C's father → D is C's parent (one generation above C)
• E is D's mother → E is D's parent (two generations above C)

Now trace A to D: A is the daughter of C, and D is C's father. Therefore, A is D's granddaughter.

**Answer:** Granddaughter

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**Example 3:** Introducing Sonia, Aarav says, "She is the wife of the only nephew of the only brother of my mother." How is Sonia related to Aarav?

**Solution:**

• "Only brother of my mother" = Aarav's maternal uncle
• "Only nephew of my maternal uncle" = The son of Aarav's mother (since the uncle's only nephew must be his sister's son). That means Aarav himself (if male) OR Aarav's brother.
• Typically in such puzzles, "only nephew" refers to the speaker if the speaker is male. So the nephew is Aarav.
• "She is the wife of Aarav" = Sonia is Aarav's wife.

**Answer:** Wife

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**Example 4:** If A + B means A is the brother of B; A – B means A is the sister of B; A × B means A is the father of B; A ÷ B means A is the mother of B. Which of the following means P is the maternal uncle of Q?

Options: (a) P + R ÷ Q (b) P – R ÷ Q (c) Q ÷ R + P (d) Q – R ÷ P

**Solution:** Maternal uncle = mother's brother. So we need: P is brother of R, and R is mother of Q.

• P + R means P is brother of R
• R ÷ Q means R is mother of Q

Combining: P + R ÷ Q means P is the brother of R, who is the mother of Q → P is Q's maternal uncle.

**Answer:** (a)

Common Mistakes

• **Confusing paternal and maternal sides**: "Uncle" without qualifier is ambiguous. If the problem says "my mother's brother," that's maternal uncle, not paternal. Always track which parent's side the relation comes from.

• **Ignoring gender clues**: "Only son" vs. "only daughter" vs. "only child" have different meanings. "Only son" means no other sons but may have daughters. Students often assume "only son" means "only child."

• **Misreading in-law relations**: Brother-in-law has two meanings — your spouse's brother OR your sister's husband. Context usually clarifies, but if you assume only one meaning, you'll miss the answer.

• **Skipping diagram for complex chains**: Trying to solve "A's father's sister's son's wife" mentally leads to errors. Draw a simple tree: A → A's father → father's sister (aunt) → aunt's son (cousin) → cousin's wife (cousin's wife or cousin-in-law). Takes 10 seconds, saves re-reading.

• **Forgetting symmetry**: If the problem states "X is Y's brother," students sometimes conclude "Y is X's brother." But Y could be X's sister. Always confirm gender before finalizing the reverse relationship.

Quick Reference

• **Paternal** = father's side; **Maternal** = mother's side. Never mix them.
• **In-laws** are created by marriage: son-in-law, brother-in-law, etc.
• **Uncle/aunt's children** = cousins. Your **sibling's children** = nephew/niece.
• **Draw diagrams** for chains longer than two steps. Use M/F or symbols (△ male, ○ female).
• **"Only son/daughter"** does NOT mean only child unless explicitly stated as "only child."
• **Practice symbolic relation problems** (A + B, A × B notation) separately — they appear frequently in RRB NTPC and require decoding the symbol key first.