Episode 8 — Aptitude and Reasoning / 8.21 — Blood Relation

8.21.b Tips, Tricks, and Shortcuts -- Blood Relation

Tip 1: The Family Tree Diagram Method (Most Important!)

ALWAYS draw a family tree for every blood relation problem. This single technique solves 95% of problems.

Standard Family Tree Drawing Rules:

  CONVENTIONS:
  
  1. Males:    Write name normally         (e.g., Rahul)
  2. Females:  Write name with (F) marker  (e.g., Sita(F))
               OR underline / circle the name
  
  3. Marriage: Horizontal double line
               Husband ==== Wife
  
  4. Parent-Child: Vertical line going DOWN
               Parent
                 |
               Child
  
  5. Siblings: Branch from same parent line
               Parent
                 |
            +----+----+
            |         |
          Child1    Child2
  
  6. Generation: Keep same generation on SAME horizontal level
  
  7. Male on LEFT, Female on RIGHT (convention)

Building the Tree Step-by-Step:

  1. Read the entire problem first.
  2. Identify the key person (usually the one asking or being asked about).
  3. Start drawing from the oldest generation mentioned.
  4. Add relationships one statement at a time.
  5. Mark gender clearly for every person.
  6. After completing the tree, answer the question.

Tip 2: Gender Identification Shortcuts

Words That Confirm MALE:

  • He, him, his, himself
  • Father, son, brother, uncle, nephew
  • Grandfather, grandson, husband
  • Man, boy, gentleman
  • King, prince, actor, hero

Words That Confirm FEMALE:

  • She, her, herself
  • Mother, daughter, sister, aunt, niece
  • Grandmother, granddaughter, wife
  • Woman, girl, lady
  • Queen, princess, actress, heroine

Words That Do NOT Confirm Gender:

  • Cousin, child, parent, spouse, sibling
  • Doctor, engineer, teacher, friend
  • Person, individual, they, them (in modern usage)

Trap Warning:

Many questions deliberately use gender-neutral terms like "child," "cousin," or "doctor" to create confusion. Do NOT assume gender unless stated.

Tip 3: The "Chain Reduction" Method

When a problem gives a long chain of relationships, simplify step by step.

Example:

"A's father's mother's husband's son's wife"

Chain:

  A
  -> father's          = A's Father
  -> mother's          = A's Paternal Grandmother
  -> husband's         = A's Paternal Grandfather
  -> son's             = A's Father or Uncle
  -> wife              = A's Mother or Aunt

Simplification Rules:

  X's father's father    = X's grandfather
  X's mother's mother    = X's grandmother (maternal)
  X's father's wife      = X's mother (usually)
  X's mother's husband   = X's father (usually)
  X's brother's father   = X's father
  X's sister's mother    = X's mother
  X's father's son       = X's brother (or X himself)
  X's mother's daughter  = X's sister (or X herself)

Tip 4: The "Only" Keyword Trick

When you see "only" in a blood relation problem, it ELIMINATES possibilities:

StatementWhat It Eliminates
"A's father's only son"A has no brothers -> this person IS A (if male)
"A's mother's only daughter"A has no sisters -> this person IS A (if female)
"A's only child"A has exactly 1 child, no siblings for the child
"Only son of A's father"A's father has 1 son -> that son is A (if A is male)
"Only daughter of A's mother"A's mother has 1 daughter -> that daughter is A (if A is female)

Critical Shortcut:

"X's father's only son" = X himself (if X is male and has no brothers).

Tip 5: Coded Relationship -- Substitution Method

Step 1: Write the code table clearly

  Example:
  + = Father     - = Mother
  * = Brother    / = Sister
  = = Spouse     ^ = Son
  # = Daughter

Step 2: Replace codes one at a time

Step 3: Build mini family tree

Example:

If A + B * C, how is A related to C?

  A + B  ->  A is father of B
  B * C  ->  B is brother of C

  Family tree:
       A
       |
    +--+--+
    |     |
    B     C

  A is the FATHER of C.

Tip 6: "Pointing to a Photograph" -- Standard Approach

Template:

"Pointing to [person X], A says, 'He/She is the [relation] of my [relation].'"

Solving:

  1. Start from A (the speaker).
  2. Trace "my [relation]" first -> find that intermediate person.
  3. Then find "[relation] of" that person -> that is person X.
  4. Determine X's relationship to A.

Example:

"Pointing to a girl, Ram says, 'She is the daughter of the only son of my grandfather.'"

  Step 1: Ram's grandfather -> one generation up from Ram's father
  Step 2: Only son of grandfather -> Ram's father (only son)
  Step 3: Daughter of Ram's father -> Ram's sister

  The girl is Ram's SISTER.

Tip 7: Two-Way Relationship Reading

If A is B's father, then B is A's son/daughter. Always check both directions:

If A is B's...Then B is A's...
FatherSon / Daughter
MotherSon / Daughter
SonFather / Mother
DaughterFather / Mother
BrotherBrother / Sister
SisterBrother / Sister
UncleNephew / Niece
AuntNephew / Niece
NephewUncle / Aunt
NieceUncle / Aunt
GrandfatherGrandson / Granddaughter
GrandmotherGrandson / Granddaughter
HusbandWife
WifeHusband
Father-in-lawSon-in-law / Daughter-in-law
Mother-in-lawSon-in-law / Daughter-in-law

Tip 8: Handling Complex Problems with Multiple People

Strategy: Number the statements and process sequentially.

Example:

"A is B's father. C is A's mother. D is C's husband. E is D's son."

  Statement 1: A is B's father
       A
       |
       B

  Statement 2: C is A's mother
       C
       |
       A
       |
       B

  Statement 3: D is C's husband
       D ==== C
                |
                A
                |
                B

  Statement 4: E is D's son
       D ==== C
         |        |
         E        A
                  |
                  B

  Now: E is A's brother (or half-brother through D).
       E is B's uncle.

Tip 9: Generation Counting Shortcut

To quickly determine the relationship, count the generation gap:

  Same generation (gap = 0):
    Brother, Sister, Cousin, Spouse, Brother/Sister-in-law

  One generation up (gap = +1):
    Father, Mother, Uncle, Aunt, Father/Mother-in-law

  One generation down (gap = -1):
    Son, Daughter, Nephew, Niece, Son/Daughter-in-law

  Two generations up (gap = +2):
    Grandfather, Grandmother

  Two generations down (gap = -2):
    Grandson, Granddaughter

Quick Check:

If you trace from person A to person B and go UP 1 and DOWN 0, the gap is +1, so B is in a "parent/uncle/aunt" role to A.

Tip 10: Common Exam Traps

Trap 1: Assuming gender from names

  • "Kiran" can be male or female in India.
  • "Kim" can be male or female.
  • Only trust explicit gender markers (he/she, son/daughter, etc.).

Trap 2: "Brother of father" vs. "Father's brother's son"

  • Brother of father = Uncle
  • Father's brother's son = Cousin
  • These are DIFFERENT relationships.

Trap 3: "Mother-in-law" ambiguity

  • Your mother-in-law = your spouse's mother.
  • Your daughter-in-law's mother-in-law = YOU (if you are the mother) or your wife.

Trap 4: Forgetting the "self" possibility

  • "My father's son" could be "my brother" OR "myself."
  • Context determines which one.

Trap 5: Multiple possible answers

  • Some problems genuinely have two possible answers (e.g., "uncle or father").
  • Choose "Cannot be determined" if it's an option, or pick the most specific answer.

Tip 11: Speed Strategy

Problem TypeTime TargetMethod
Simple 2-person15-20 secMental tracing
Photograph pointing30-45 secChain reduction
3-4 person family45-60 secQuick tree sketch
5+ person family60-90 secFull family tree
Coded relationship45-60 secSubstitution + tree
Complex puzzles (sets)3-5 minDetailed tree diagram

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