Blood Relations

Blood-relation questions sit on a small family tree with three or four generations: grandparents, parents, the people in the puzzle, and sometimes their children.

Every question is really asking you to follow a path along that tree. The work is to build the tree correctly from the wording; once it is drawn, the answer is a short walk from one person to another. Nothing depends on names or ages unless the puzzle states them.

• Paternal means on the father's side, maternal on the mother's side. Your father's brother is your paternal uncle; your mother's brother is your maternal uncle.
• In-laws come through marriage: your spouse's brother and your sister's husband are both your brother-in-law; your son's wife is your daughter-in-law.
• Nephew and niece are your sibling's children. Your cousin is your uncle's or aunt's child.
• Sibling covers brother or sister without stating which. Spouse covers husband or wife.
• Two people are of the same generation if the same number of parent-steps separates each from a shared ancestor.

Use one fixed set of marks so the picture never lies:

• A triangle for a male, a circle for a female, a plain box when the sex is unknown.
• A double line between two people who are married.
• A vertical line dropping to their children, with siblings side by side on one level.
• Keep every person of one generation on the same horizontal level, parents above, children below.

     A --=-- B          double line = married
         |
    +----+----+         vertical line = children
    C         D          C and D on one level = siblings

Add each fact to the diagram as you read it, and never carry a half-formed picture in your head.

A speaker points at someone and describes them through a chain like "the only son of my grandfather's daughter". Work the chain from the far end back to the speaker:

1. Start at the last noun ("my grandfather") and move outward one link at a time.
2. Replace every "my" and "I" with the speaker once the chain is built.
3. Use words like "only" — "the only daughter of X" tells you X has no other daughters, which often pins the person down.
4. Read the relationship of that person to the speaker off the finished diagram.

Here each symbol fixes one relationship, and you are handed an expression to evaluate. A common key is:

• A + B means A is the father of B.
• A - B means A is the mother of B.
• A * B means A is the brother of B.
• A / B means A is the sister of B.

Build the expression left to right, one link at a time, drawing each into the diagram. The final question — say, how A relates to the last person — is then read straight off the picture. The sex of the end person is often not needed for the answer.

1. Pointing. Pointing at a boy, Meera says, "His mother is the only daughter of my mother's father." How is the boy related to Meera?

Start at the far end: "my mother's father" is Meera's maternal grandfather. "The only daughter of" him — since he has just one daughter, and Meera's mother is a daughter of his — is Meera's mother. So the boy's mother is Meera's mother, which makes the boy Meera's brother.

2. Coded. With + for father, - for mother, * for brother, evaluate P + Q - R * S and state how P relates to S.

P + Q: P is Q's father. Q - R: Q is R's mother. R * S: R is S's brother, so R and S share the parent Q. Q is the mother of S, and P is the father of Q. P is therefore the father of S's mother, that is, S's maternal grandfather.

Key for the coded items: + father, - mother, * brother, / sister. Give the answer and a one-line reason.

1. A - B + C: how is A related to C?
2. M * N - O: how is M related to O?
3. P / Q * R: how is P related to R?
4. Pointing at a woman, Rohan says, "She is the daughter of my father's only son." Rohan has no brothers. Who is she to Rohan?
5. "Sudha's father is my father's son, and I have no brothers or sisters." How is the speaker related to Sudha?
6. X + Y / Z: how is X related to Z?
7. K is the son of L. L is the sister of M. M is married to N. How is K related to N?