Blood Relations – Reasoning Ability
(Bihar Police Sub‑Inspector – Reasoning Ability – Blood Relations)
1. Simple Explanation
Blood‑relation problems ask you to determine the relationship between two persons in a family tree.
- Direct lineage – ancestor → descendant (parent, child, grand‑parent, etc.)
- Collateral lineage – relatives on the same generational level: siblings, cousins, aunts, uncles.
- Spousal relations – wife, husband, in‑law, etc.
The goal is to place each person in the correct generational slot and then read the relationship.
2. Key Points
| Point | What to Remember |
|---|---|
| Naming conventions | P = Person, P1, P2… = given names. |
| Generational levels | Level 0 = the person referenced (e.g., P). Level +1 = child, –1 = parent, +2 = grand‑child, –2 = grand‑parent, etc. |
| Sibling relation | Same level, share the same parents. |
| Cousin types | 1st cousin: share grandparents; 2nd cousin: share great‑grandparents; etc. |
| In‑law relations | Husband/Wife = spouse; mother‑in‑law = mother of spouse; father‑in‑law = father of spouse; son‑in‑law = husband of daughter or son of spouse. |
| Common abbreviations | M = Mother, F = Father, S = Sister, B = Brother, A = Aunt, U = Uncle, C = Cousin. |
| Direction of edges | Use “→” for child, “←” for parent. |
| Avoid double counting | A person can be both a son‑in‑law and a nephew‑in‑law; choose the first applicable relation. |
| Use a diagram | Sketching a quick tree often saves confusion. |
3. Worked Example
Question (Typical)
In a family,
Ris the daughter ofS.Tis the son ofR.Uis the mother ofS.
What is the relationship ofUtoT?
Step 1 – Build the tree
U (mother)
└─ S (child of U)
└─ R (daughter of S)
└─ T (son of R)
Step 2 – Count generational steps from U to T
U → S: +1 (child)S → R: +1 (child)R → T: +1 (child)
Total steps = +3.
So, U is great‑grandmother of T.
Step 3 – Verify against options
If options are:
A) Grandmother
B) Great‑Grandmother
C) Aunt
D) Mother
Correct answer: B) Great‑Grandmother.
4. Quick Revision Summary
| Category | Typical Questions | Quick Tips |
|---|---|---|
| Direct lineage | Who is the mother/father of X? | Count steps up (←) or down (→). |
| Collateral | Who is the sibling/uncle/aunt of X? | Same level = sibling; one level higher = parent; same level but different parents = cousin. |
| Cousins | Identify 1st, 2nd, 3rd cousins. | Count how many generational steps are needed to reach a common ancestor; subtract 1. |
| In‑laws | Who is the father‑in‑law, son‑in‑law of X? | Think of spouse’s parents or spouse’s siblings. |
| Multiple clues | Combine statements to deduce chain. | Draw a quick tree; label levels; cross‑check with all statements. |
Tip for fast solving:
- Label levels – start from the person given.
- Track direction – up for parent, down for child.
- Check for synonyms – “son‑in‑law” can also be “brother‑in‑law” depending on gender.
- Eliminate impossibilities – e.g., a person can’t be both a son and a daughter of the same person.
With practice, you’ll be able to solve even the most convoluted blood‑relation questions in seconds!