Blood Relations – Reasoning Ability
Program: Chandigarh Police – Sub‑Inspector (SI)
Section: Reasoning Ability – Blood Relations
1. Simple Explanation
Blood‑relation problems ask you to determine the kinship between two persons in a family tree, based on the rules of Indian/Western kinship.
You are given a set of statements such as:
- “A is the daughter of B.”
- “C is the brother of D.”
From these, you must deduce how two individuals are related (e.g., mother, aunt, nephew, cousin, grandfather, etc.).
Key Rules to Remember
| Rule | Description | Example |
|---|---|---|
| Direction of relation | The relation is directed – “X is Y’s father” is not the same as “Y is X’s father”. | If A is the son of B, then B is the father of A. |
| Reciprocity | Some relations are reciprocal, others are not. | A is B’s sibling ↔ B is A’s sibling. |
| Transitivity | You can chain relations: if A is B’s parent and B is C’s sibling, then A is C’s uncle/aunt. | A → B (parent), B ↔ C (sibling) → A → C (uncle/aunt). |
| Gender matters | Many terms are gender‑specific (mother, father, son, daughter, brother, sister). | “Son of” is different from “daughter of”. |
| Multiple paths | If two paths exist, choose the one that satisfies all given statements. | Two different chains leading to the same person must be consistent. |
| Terminology | Familiarise with common kinship terms: grandparent, great‑grandparent, cousin, nephew, niece, in‑law, step‑, half‑ relations. | “Grandfather” = father of a parent. |
2. Key Points (What to Focus On)
- Identify all given relationships – write them in a diagram or list.
- Break down complex relations into basic ones (parent, sibling, spouse).
- Use transitive property to chain relations step‑by‑step.
- Check consistency – if a path contradicts another statement, discard it.
- Pay attention to gender – it can change the answer (e.g., son vs daughter).
- Count the number of generational steps – e.g., two steps up = grandparent, three steps = great‑grandparent.
- Remember non‑reciprocal relations – father and son are not reciprocal.
- Watch for “in‑law” and “step” relations – they are usually explicitly mentioned.
3. Worked Example
Problem Statement
In a family tree, the following relationships are known:
- A is the daughter of B.
- B is the son of C.
- C is the brother of D.
- D is married to E.
- E is the mother of F.
- F is the sister of G.
Question: What is the relation of G to A?
Step‑by‑Step Solution
| Step | Relation | Explanation |
|---|---|---|
| 1 | A → child of B (daughter) | Given (1). |
| 2 | B → child of C (son) | Given (2). |
| 3 | C → sibling of D (brother) | Given (3). |
| 4 | D ↔ E (married) | Given (4). |
| 5 | E → child of D (mother) | Given (5). |
| 6 | F ↔ G (sisters) | Given (6). |
| 7 | F → child of E (daughter) | From (5). |
| 8 | E → spouse of D | From (4). |
| 9 | D → sibling of C | From (3). |
| 10 | C → parent of B | From (2) reversed. |
| 11 | C → parent of B → parent of A (grandparent) | Chain: C → B → A. |
| 12 | D → sibling of C → grandparent of A (great‑grandparent) | Because D is sibling of C, D is the great‑grandparent of A. |
| 13 | E → child of D → great‑grandchild of C → great‑grandchild of A? | But we need G → A. |
| 14 | F → child of E → great‑grandchild of D → great‑grandchild of C → great‑grandchild of A | Not necessary. |
| 15 | G ↔ F (sisters) → same relations as F to A. | So G is also great‑granddaughter of A. |
| 16 | Answer | G is the great‑granddaughter of A. |
Explanation of Final Relation
- A → B (daughter) → C (parent) → D (sibling) → E (spouse) → F (daughter) → G (daughter).
- Counting generational steps from A to G:
- A → B (1 step)
- B → C (2 steps)
- C → D (3 steps; D is sibling