Q.Arun said, "Ishika is the daughter of my mother's daughter". How is Arun related to Ishika?

Blood Relations — The Logic of Family Trees

You already know what a family is. The trick in blood relation problems is that you are given a set of statements about who is related to whom, and you must figure out a specific relationship — or answer a question like "How is A related to B?" — without ever seeing the people.

The entire subject rests on one skill: building a family tree in your head (or on paper) from verbal clues.

The Intuition

Imagine you hear: "Ravi is the son of Sunita. Sunita is the sister of Vikram." You instantly know Ravi is Vikram's nephew. How? Because you mentally connected the two facts. That's all a blood relation problem ever does — it gives you a chain of such statements, sometimes with a twist (in-laws, multiple generations), and asks you to walk that chain.

The difficulty comes from two things:

• The statements are not always in chronological or generational order.
• The same person may be referred to by different descriptions ("my mother's brother" vs "my uncle").

The Precise Method

Every blood relation problem reduces to constructing a family tree using these rules:

The standard relations are:

From these, you derive everything else:

• Uncle: brother of a parent
• Aunt: sister of a parent
• Nephew: son of a sibling
• Niece: daughter of a sibling
• Cousin: child of a parent's sibling
• Grandfather/Grandmother: parent of a parent
• Sibling-in-law: sibling of a spouse, or spouse of a sibling

The Step-by-Step Process

Step 1: Identify all distinct persons mentioned. Give each a symbol (A, B, C, ... or use the names given).

Step 2: Start with the most concrete statement. Usually a statement like "X is the father of Y" gives you a clear parent-child link. Draw it.

Step 3: Add each new statement to your tree. Use these conventions:

• Horizontal line — for marriage
• Vertical line | for parent-child
• Same level = same generation

Step 4: Mark gender. Use (M) and (F) or a symbol convention (square for male, circle for female).

Step 5: When stuck, work backwards. If the question asks "How is P related to Q?" and you have statements about P and about Q, try to connect them through a common person.

A Worked Example

Problem: A is the brother of B. C is the daughter of A. D is the sister of C. How is D related to B?

Step 1: Persons: A, B, C, D.

Step 2: "A is the brother of B" → A and B are siblings. A is male. B's gender unknown.

Step 3: "C is the daughter of A" → A is father of C. C is female.

Step 4: "D is the sister of C" → C and D are siblings, both children of A. D is female.

Tree:

        A (M) — (spouse, not named)
         |
    ┌────┴────┐
    C (F)    D (F)
    
    B (sibling of A, gender ?)

Step 5: D is the daughter of A. B is the sibling of A. Therefore D is the niece of B.

Common Traps

Trap 1: Assuming gender. "A is the parent of B" does not tell you if A is father or mother. You need another clue.

Trap 2: Only child. If a statement says "A is the brother of B", it implies A and B share at least one parent. But it does not mean they have no other siblings.

Trap 3: In-laws. "A is the wife of B's brother" means A is married to B's brother, so A is B's sister-in-law. Notice the chain: B → brother → wife.

Trap 4: Multiple generations. "A is the grandfather of C" means there is a parent (say B) between them. You must place B in the tree.

Why This Works

Blood relation problems test structured thinking, not memory. Every statement is a logical constraint. By drawing the tree, you convert verbal constraints into a visual structure where relationships become obvious. The same skill applies to puzzles, data sufficiency, and even some coding problems.