Blood relations: draw it, don't guess

Solve blood relation questions reliably with a simple family-tree notation, the relation words you need, and worked examples, from one-line puzzles to coded relations.

Blood relation questions describe a family in a sentence or two and ask how two people are related. They feel tricky because you have to keep several people in your head at once. The fix is simple: don't keep them in your head. Draw a small family tree as you read, and the answer usually becomes obvious.

The notation

Use a quick, consistent way of drawing. One common system:

• Put each generation on its own row: grandparents at the top, then parents, then children.
• Mark males with + and females with − (or use squares and circles).
• Join husband and wife with a double line (=).
• Join brothers and sisters with a horizontal line.
• Join parents to children with a vertical line.

Write the sex next to each name as soon as the question tells you. Many wrong answers come from guessing whether someone is male or female.

The words you need

Worked example 1

Riya is Harish's daughter. Harish is Farhan's brother. How is Riya related to Farhan?

1. Harish (+) is Riya's (−) father, so Harish is one row above Riya.
2. Farhan (+) is Harish's brother, so Farhan is on the same row as Harish.
3. Riya is Farhan's brother's daughter, which makes her Farhan's niece.

Worked example 2

Pointing to a man, Meera says, "His mother is the only daughter of my mother." How is the man related to Meera?

1. "The only daughter of my mother" is Meera herself (Meera is female, and she is her mother's only daughter).
2. So the man's mother is Meera.
3. The man is Meera's son.

The phrase "only daughter of my mother" is a classic trick. Whenever a statement loops back to the speaker, check whether it simply means the speaker.

Worked example 3

A is B's sister. C is B's mother. D is C's father. E is D's mother. How is A related to D?

Draw it row by row:

• E (−) at the top.
• D (+), E's son, on the next row.
• C (−), D's daughter, below D.
• A (−) and B, C's children, on the bottom row.

A is D's daughter's daughter, so A is D's granddaughter.

Coded relations

Some questions code the relations with symbols, for example "P + Q means P is the father of Q, P × Q means P is the sister of Q." Treat these exactly the same way: translate each symbol into words first, draw the tree, then answer. Don't try to work with the symbols directly.

A checklist

1. Read one statement at a time and add it to the drawing straight away.
2. Note each person's sex as soon as it's given, and leave it blank if it isn't.
3. Watch for statements that loop back to the speaker.
4. Read the question from the right person's point of view: "A is B's ___" is not the same as "B is A's ___".
5. If a person's sex is never given, an answer like "brother" or "sister" may not be certain. Choose "cannot be determined" only if it really can't be worked out.

Practise

Try the solved blood relations examples. Direction sense questions reward the same habit of drawing as you read.

Practise it: solved examples.