Blood relations for SBI PO

Blood relations look easy because everyone has a family. That is exactly the problem. Candidates answer from instinct ("the mother's brother is the uncle, obviously") and skip the question that matters: what does the clue actually state? In SBI PO, the clues are built so that one person's gender, or one link in the tree, is left open on purpose.

The method below keeps you honest: draw every relation, mark gender only when a word states it, and let "cannot be determined" be a real answer.

How it is asked

• Family puzzles: six to eight people across two or three generations, with four or five questions on the finished tree. These are more common in the mains.
• Coded relations: symbols such as @ and # stand for "father of", "sister of" and so on, and you decode a chain.
• Pointing questions: "Pointing to a photograph, a man says…" One sentence, one relation to unwind.
• Relations inside puzzles: seating or floor puzzles that add "A's daughter sits…" as a clue.

Drawing the tree

Words that state gender: father, mother, son, daughter, brother, sister, husband, wife, uncle, aunt, nephew, niece, grandfather, grandmother, grandson, granddaughter, son-in-law, daughter-in-law.

Words that do not: child, sibling, parent, spouse, cousin, grandchild, and every name or letter.

Relation vocabulary you must know

The method

1. Read one clue at a time and draw it at once.
2. Mark gender only from the relation words above.
3. Place generations as soon as a parent or grandparent relation appears.
4. Use in-law clues last. They often decide who is married to whom.
5. Answer from the tree, and say "cannot be determined" whenever the answer needs a gender or link you do not have.

Unless a question says otherwise, assume each person has at most one spouse and that siblings share both parents. These are the standard exam conventions.

A worked family puzzle

Eight people, J, K, L, M, N, O, P and Q, belong to one family.

1. J is the father of L and M, and K is their mother.
2. L is the sister of M.
3. N is the son-in-law of K.
4. Q is the husband of L.
5. O and P are the children of N and his wife.
6. O is a son.

Step 1. Clue 1: J is male, K is female, and they are married. L and M are their children. Neither child's gender is known yet.

Step 2. Clue 2: "sister" makes L female. M is still open.

Step 3. Clue 4: Q is male and married to L.

Step 4. Clue 3: N is male and married to a daughter of K. L is already married to Q, so N's wife is M. That makes M female, stated through "son-in-law", not guessed.

Step 5. Clues 5 and 6: O and P are the children of N and M. O is male. P's gender is never stated.

Questions:

1. How is K related to P? Grandmother.
2. How is Q related to M? Brother-in-law. He is the husband of M's sister.
3. How is L related to O? Maternal aunt. L is the sister of O's mother.
4. How is N related to J? Son-in-law.
5. How is P related to J? Grandchild. "Grandson" or "granddaughter" cannot be determined.
6. How many people are definitely female? Three: K, L and M.

Coded relations

Example 1. P # Q $ R. How is P related to R?

• P is the mother of Q. Q is the brother of R. So R is also P's child.
• P is R's mother. R's gender is not stated, so you cannot say son or daughter.

Example 2. Which expression shows that X is the grandfather of Z?

• (a) X & Y # Z: X is the husband of Z's mother, so X is Z's father.
• (b) X @ Y # Z: X is the father of Y, and Y is Z's mother. X is Z's maternal grandfather.
• (c) X @ Y $ Z: X is the father of Y, and Y is Z's brother, so X is Z's father.
• (d) X $ Y @ Z: X is the brother of Z's father, so X is Z's paternal uncle.
• Answer: (b).

Pointing questions

Example 3. Pointing to a woman, a man says, "Her mother is the only daughter of my mother." How is the man related to the woman?

• The man's mother's only daughter is the man's sister. He is male, so it cannot be him.
• The woman's mother is his sister. He is her maternal uncle.

Example 4. Pointing to a boy, a woman says, "He is the son of my father's only son." How is the boy related to the woman?

• Her father's only son is her brother. She is female, so it cannot be her.
• The boy is her brother's son. He is her nephew.

Practice set

Questions 1 and 2 use the worked family. Questions 3 to 5 use the codes above.

1. How is L related to P?
2. How is J related to O?
3. What does A $ B # C tell you about A and C?
4. What does X & Y % Z tell you about X and Z?
5. What does T @ S & R tell you about R and T?
6. Pointing to a girl, a man says, "She is the daughter of the only child of my father." How is the girl related to the man?
7. A is the brother of B. B is the sister of C. C is the father of D. How is A related to D?
8. E is a child of F. F is the only sibling of G. G is male. How is E related to G?

Answers:

1. Aunt (maternal). L is female and is the sister of P's mother, M.
2. Grandfather (maternal). J is the father of O's mother.
3. A is C's maternal uncle. A is the brother of B, and B is C's mother.
4. X is Z's brother-in-law. X is the husband of Z's sister.
5. R is T's daughter-in-law. T is the father of S, and S is the husband of R. So S is T's son and R, as his wife, is T's daughter-in-law.
6. Daughter. The only child of the man's father is the man himself.
7. Paternal uncle. A, B and C are siblings; A is male and C is D's father.
8. Nephew or niece; cannot be determined. G is E's uncle, but E's gender is never stated.

What to do next

• Redraw the worked family from a blank page and answer all six questions without looking.
• Solve one family puzzle and ten coded questions a day for a week.
• Write (?) beside every person whose gender is not stated, every single time.
• The same tree-drawing discipline helps in data sufficiency, where blood-relation statements are common. See the reasoning plan for scheduling.