**CAT DILR: Family Tree & Relationship Logic – The 99%ile Study Guide**

CAT DILR: Family Tree & Relationship Logic – The 99%ile Study Guide

What This Is

Family Tree & Relationship Logic questions test your ability to decode complex blood and marital relationships from limited information. They appear 2–3 times per CAT in the DILR section, often as part of a larger set (e.g., 4–5 questions on a single family tree). Mastering this topic gives you easy 8–12 marks with minimal calculation—pure logic. A typical CAT question:

"A is the brother of B. C is the father of A. D is the sister of C. E is the mother of D. How is B related to E?"

If you can solve this in under 30 seconds, you’re on track for 99%ile. If not, this guide will get you there.

Key Concepts & Techniques

1. Gender-Specific Terms
2. Brother/Sister: Same parents.
3. Uncle/Aunt: Parent’s sibling (or spouse of parent’s sibling).
4. Niece/Nephew: Child of sibling (or sibling’s spouse).
5. Cousin: Child of parent’s sibling.
6. In-laws: Spouse’s relatives or relatives’ spouses.

7. When to use: Always label genders first. A "sibling" without gender is a trap—CAT will test if you assume.

8. Marriage vs. Blood Relations

9. Marriage: Creates "in-law" relationships (e.g., wife’s brother = brother-in-law).
10. Blood: Direct lineage (parent, child, sibling).

11. When to use: Draw double lines (====) for marriage, single lines (—) for blood. Prevents mixing up in-laws with blood relatives.

12. Generation Tracking

13. Up: Parent, grandparent, great-grandparent.
14. Down: Child, grandchild, great-grandchild.
15. Same generation: Sibling, cousin, spouse.

16. When to use: Assign generation numbers (e.g., +1 for parent, -1 for child) to avoid confusion in multi-generation trees.

17. Option Elimination (MCQ Only)

18. If options are "A is the X of B," test each option by reversing the relationship (e.g., if "A is the uncle of B," check if "B is the nephew/niece of A").

19. When to use: In MCQ questions, eliminate impossible options first (e.g., if A is male, "mother" is invalid).

20. Symbolic Notation

21. M/F: Male/Female.
22. →: Parent to child (e.g., C → A means C is parent of A).
23. =: Marriage (e.g., A = B means A is married to B).

24. When to use: Always draw symbols—saves time and reduces errors.

25. Negative Information

26. "A is not the mother of B" → A could be father, aunt, uncle, etc.
27. "B has no siblings" → B’s only possible relatives are parents, spouse, or children.

28. When to use: CAT often gives negative clues—use them to eliminate possibilities.

29. Step-Relatives

30. Step-parent: Parent’s new spouse (not blood-related).
31. Step-sibling: Child of step-parent (not blood-related).

32. When to use: If the question mentions "step," do not assume blood relation.

33. Adoption & Half-Relatives

34. Adopted child: Treated as blood relative in CAT (unless specified otherwise).
35. Half-sibling: One common parent.
36. When to use: CAT rarely tests adoption, but if it does, assume blood relation unless stated.

Step-by-Step Strategy

Follow this exact process for every question:

Step 1: Read the Question Twice

• First read: Understand the final question (e.g., "How is X related to Y?").
• Second read: Note all given relationships (e.g., "A is the brother of B").

Step 2: Assign Genders & Symbols

• For every person, write M/F based on given info (e.g., "brother" → M, "sister" → F).
• Use → for parent-child, = for marriage, — for siblings.

Step 3: Draw the Tree

• Start with the oldest generation (parents/grandparents).
• Work downwards to children.
• Label all genders (even if not directly given).

Step 4: Fill Missing Links

• Use negative info (e.g., "A is not the mother of B" → A could be father).
• Use generation logic (e.g., if A is parent of B, B cannot be parent of A).

Step 5: Answer the Question

• Trace the shortest path between the two people in question.
• Reverse the relationship if needed (e.g., if "X is the uncle of Y," then "Y is the nephew/niece of X").

Step 6: Verify with Options (MCQ Only)

• If MCQ, test each option by reversing the relationship.
• Eliminate impossible options (e.g., if X is male, "mother" is invalid).

Fully Worked CAT-Style Example

Question:
"P is the brother of Q. R is the father of P. S is the sister of R. T is the mother of S. How is Q related to T?"

Step 1: Read Twice

• Final question: How is Q related to T?
• Given:
• P is brother of Q.
• R is father of P.
• S is sister of R.
• T is mother of S.

Step 2: Assign Genders & Symbols

• P: M (brother)
• Q: ? (sibling of P → could be M/F, but no info → keep as ?)
• R: M (father)
• S: F (sister)
• T: F (mother)

Step 3: Draw the Tree

T (F)
|
S (F) — R (M)
      |
     P (M) — Q (?)

• T is mother of S.
• S is sister of R → R is son of T.
• R is father of P → P is son of R.
• P is brother of Q → Q is sibling of P (child of R).

Step 4: Fill Missing Links

• Q is child of R (since P and Q are siblings, and R is father of P).
• R is son of T → Q is grandchild of T.

Step 5: Answer the Question

• Q is the grandchild of T.
• But options may say "grandson/granddaughter." Since Q’s gender is unknown, the most accurate answer is "grandchild."
• If options are:
• Grandson
• Granddaughter
• Grandchild
• Daughter
• Correct answer: 3 (Grandchild).

Step 6: Verify (MCQ)

• If Q is grandson → Q is male → but no info on Q’s gender → invalid.
• If Q is granddaughter → Q is female → invalid.
• "Grandchild" is gender-neutral → correct.

Common Mistakes

1. Mistake: Assuming Gender
2. Why it happens: "Sibling" is gender-neutral, but students assume "brother" or "sister."

3. Correct approach: Never assume gender unless explicitly given. Use "?" in your tree.

4. Mistake: Mixing Blood and Marriage

5. Why it happens: Confusing "brother-in-law" (spouse’s brother) with "brother" (blood).

6. Correct approach: Double lines (====) for marriage, single lines (—) for blood.

7. Mistake: Ignoring Negative Info

8. Why it happens: Skipping clues like "A is not the mother of B."

9. Correct approach: Use negative info to eliminate possibilities (e.g., if A is not mother, A could be father, aunt, etc.).

10. Mistake: Generation Errors

11. Why it happens: Misplacing people in generations (e.g., thinking grandparent is parent).

12. Correct approach: Assign generation numbers (+1 for parent, -1 for child).

13. Mistake: Overcomplicating Step-Relatives

14. Why it happens: Assuming step-relatives are blood-related.
15. Correct approach: Step-relatives are not blood-related unless specified.

CAT Traps & Time Management

Traps:

1. Gender-Neutral Terms
2. CAT uses "sibling," "child," "cousin" to hide gender. Never assume.

3. How to spot: Look for words like "brother," "sister," "son," "daughter" to confirm gender.

4. In-Law Confusion

5. "Brother-in-law" could mean:
   • Spouse’s brother.
   • Sister’s husband.

6. How to spot: Check if the relationship is via marriage (====) or blood (—).

7. Negative Clues

8. "A is not the mother of B" → A could be father, aunt, uncle, etc.

9. How to spot: CAT often gives 2–3 negative clues—use them to narrow down.

10. Multi-Generation Trees

11. CAT may give a 5–6 generation tree with 1–2 questions. Don’t draw the whole tree—focus on the path between the two people in the question.

Time Management:

• Easy question: 30–45 sec.
• Medium question: 1–1.5 min.
• Hard question: 2 min max.
• If stuck: Skip and return later—don’t waste time on one question.

Quick Practice

Question:
"A is the sister of B. C is the father of A. D is the brother of C. E is the mother of D. How is B related to E?"

Answer:
B is the grandchild of E.
Solution Path: - A (F) — B (?) - C (M) → A - D (M) — C - E (F) → D - B is child of C → grandchild of E.

Last-Minute Cram Sheet

1. Brother/Sister: Same parents → M/F.
2. Uncle/Aunt: Parent’s sibling → M/F.
3. Niece/Nephew: Sibling’s child → F/M.
4. Cousin: Parent’s sibling’s child → no gender.
5. In-laws: Spouse’s relatives → marriage (====).
6. Step-relatives: Not blood-related → unless specified.
7. Negative info: "Not mother" → could be father, aunt, etc.
8. Generation rule: +1 for parent, -1 for child.
9. MCQ trick: Reverse the relationship to test options.
10. ⚠️ Trap: "Sibling" ≠ "brother" or "sister" → gender unknown.

Final Tip:
Draw every tree—even if it seems simple. CAT’s questions look easy but are designed to trick you. Symbols + gender labels = 100% accuracy.