Blood Relations – Study Notes (SBI PO – Reasoning Ability)
Why it matters
In the SBI PO exam, blood‑relation questions test your ability to reason about family ties, deduce relationships, and work out generational differences.
Mastering the terminology and the logic behind the connections saves time and avoids errors.
1. Simple Explanation
- Blood relations are kinships that arise from a common ancestor, not by marriage.
- Every person can be placed in a family tree with two axes:
- Vertical axis – Generations (ancestor → descendant)
- Horizontal axis – Collateral (siblings, cousins, etc.)
Rule of thumb
- Up one generation = parent (father, mother)
- Down one generation = child (son, daughter)
- Same generation, different branch = sibling or cousin
2. Key Points & Terminology
| Category | Terminology | Relationship | Generational Difference |
|---|---|---|---|
| Direct lines | Father, Mother | Parent of you | –1 |
| Son, Daughter | Child of you | +1 | |
| Grand‑father / Grand‑mother | Parent’s parent | –2 | |
| Grand‑daughter / Grand‑son | Child’s child | +2 | |
| Great‑grand‑father | Grand‑parent’s parent | –3 | |
| Great‑grand‑daughter | Grandchild’s child | +3 | |
| Collateral (same generation) | Brother, Sister | Sibling | 0 |
| Uncles / Aunts | Parent’s sibling | –1 | |
| Nephews / Nieces | Sibling’s child | +1 | |
| Cousins | Children of your parents’ siblings | 0 | |
| Cousins‑once‑removed | One generation apart from cousins | ±1 | |
| Cousins‑twice‑removed | Two generations apart | ±2 | |
| Special notes | In India, cousin is often written as “first cousin” (children of siblings) | ||
| “Second cousin” = children of first cousins, and so on. | |||
| “Great‑uncle” = your grand‑parent’s sibling. |
Remember:
- The sign “–” indicates an ancestor (up the tree).
- The sign “+” indicates a descendant (down the tree).
- Zero means you are in the same generation.
3. Worked Example 1 – Classic “Find the Relationship”
Question
A is the son of B.
B is the daughter of C.
C is the sister of D.
What is the relationship between A and D?
Step‑by‑step solution
-
Map the known links
- A → B (son) → B is B’s child.
- B → C (daughter) → B is C’s child.
- C → D (sister) → C and D are siblings.
-
Determine generational positions
- Let’s place C at generation 0.
- B is C’s child → generation +1.
- A is B’s child → generation +2.
-
Position D
- D is C’s sister → same generation as C → generation 0.
-
Find the relative difference between A (+2) and D (0)
- A is two generations below D.
-
Translate to a family term
- Two generations below = grand‑daughter (if A is female) or grand‑son (if A is male).
- Since A is a son, A is D’s grandson.
Answer: D is A’s grand‑father. (Alternatively, “A is the grandson of D.”)
4. Worked Example 2 – “Remove” Word Challenge
Question
R is the mother of S.
S is the aunt of T.
T is the son of U.
What is the relationship between R and U?
Solution
| Step | Reasoning | Result |
|---|---|---|
| 1 | R → S (mother) → R is S’s parent. | R is S’s parent. |
| 2 | S → T (aunt) → S is T’s aunt → T is S’s niece/nephew. | T is S’s niece |