How to Solve Blood Relation Problems
Solve blood relation reasoning problems by drawing family trees and decoding compound relations, with worked examples and practice questions.
Expected Interview Answer
Blood relation problems are solved by drawing a family tree diagram as each clue is read, using generation levels (rows) and gender-tagged nodes, then tracing the path between the two people in question.
Draw a vertical axis for generations (grandparents, parents, children) and connect siblings horizontally, spouses with an equals sign, and parent-child links with a vertical line. Tag each person’s gender (M/F) as soon as it is known from pronouns or titles like "son", "daughter", "brother". Resolve compound relations step by step — "my father’s only son’s wife" should be decoded one relation at a time: father → his only son (which is "me" if I have no brothers, otherwise a brother) → that person’s wife. Never assume a relation not explicitly stated, since a word like "sister" can later turn out to mean "cousin sister" in some phrasings, so read carefully.
- A diagram removes the need to hold every relation in working memory
- Generation rows immediately reveal whether a relation is same-generation (sibling/cousin) or cross-generation (parent/uncle)
- Decoding compound relations one link at a time avoids logical errors
AI Mentor Explanation
Building a family tree is like building a batting partnership scorecard: you note who is at which end (generation row) and who is partnered with whom (spouse links), updating the board after every ball (clue). Just as a scorer never guesses a batter’s identity from memory but checks the board, you never guess a relation — you trace it on the diagram. A "brother of the non-striker" is found by reading the board, not recalling it, exactly as blood relations are found by reading the tree.
Worked example (family tree trace)
Grandfather
- only son = Raj's father
Raj's father
- his daughter = the woman in photo
Result
- The woman is Raj's sister
Step-by-Step Explanation
Step 1
Draw generation rows
Set up rows for grandparents, parents, and children as clues arrive.
Step 2
Tag gender as revealed
Mark M/F on each node as soon as a pronoun or title confirms it.
Step 3
Decode compound relations one link at a time
Resolve "father's only son's wife" left to right, one relation per step.
Step 4
Trace the final path
Follow the diagram from the reference person to the target person to name the relation.
What Interviewer Expects
- A systematic diagram-first approach rather than mental tracking
- Correct handling of "only son/daughter" as self-referential when no siblings are mentioned
- Careful gender tagging as soon as pronouns appear
- Step-by-step decoding of compound, nested relation phrases
Common Mistakes
- Assuming a gender without explicit evidence from the clue
- Skipping intermediate relations instead of resolving compound phrases one link at a time
- Misreading "only son/daughter" and introducing a nonexistent sibling
- Losing track of which generation row a person belongs to in longer chains
Best Answer (HR Friendly)
“I draw a small family tree as I read each clue, putting generations in rows and marking gender as soon as I know it. For a compound clue like "my father's only son's wife", I resolve it one relation at a time rather than trying to guess the answer directly. That diagram makes the final relation obvious just by tracing the path.”
Follow-up Questions
- How do you handle a clue that introduces a "cousin" without specifying which side of the family?
- What is the difference between "brother-in-law" from a spouse's side versus a sibling's spouse?
- How would you solve a problem involving a coded relation notation, like A + B means A is the mother of B?
- How do you keep track of relations when the puzzle spans four generations?
MCQ Practice
1. Pointing to a man, a woman says, "His mother is the only daughter of my mother." How is the woman related to the man?
The only daughter of the woman's mother is the woman herself, so "his mother" equals the woman — meaning the woman is the man's mother.
2. A is the son of B. B is the sister of C. C is the father of D. How is A related to D?
B and C are siblings, so their children A and D are cousins.
3. Pointing to a photo, Rahul said, "She is the daughter of my grandfather's only son." Who is she to Rahul (Rahul has no siblings)?
Grandfather's only son is Rahul's father (Rahul has no siblings, so he is the only son); father's daughter is Rahul's sister.
Flash Cards
Best strategy for blood relations? — Draw a family tree with generation rows as each clue is read.
"Only son/daughter" clue meaning? — If no other siblings are mentioned, it refers to the speaker themselves.
How to resolve compound relations? — One link at a time, left to right, never guess the final answer directly.
When are two people cousins? — When their parents are siblings of each other (same generation, different branch).