Blood relations

Blood Relations – Study Notes (Bihar Police Constable – Reasoning Ability)

1. Simple Explanation

Blood relations (consanguineous relations) are the relationships that arise by virtue of common ancestry.
They are direct (lineal) or collateral and are classified by degree (how many generations separate you from the person).

• Direct / Lineal – Parent – child – grand‑parent – grand‑child, etc.
• Collateral – Siblings, aunts, uncles, cousins, etc.
• Affinal (not blood) – spouse, in‑law, etc. (often excluded in reasoning questions).

In reasoning problems the degree matters:

• 1st degree: Parents & Children
• 2nd degree: Grand‑parents, Grand‑children, Siblings
• 3rd degree: Uncles, Aunts, Nephews, Nieces, Cousins
• 4th degree: Great‑grandparents, Great‑grandchildren, etc.

2. Key Points

How to Determine Degree

1. Count the number of edges (parent–child links) between the two persons.
2. The maximum of the two paths is the degree.
   • Example: Person A’s father → A’s brother → B. Paths: A→Father (1), Father→Brother (1) → B. Max = 2 → 2nd degree.

3. Worked Example

Problem:

In a family tree, P is the son of Q. R is the daughter of Q. S is the son of R.
What is the relation between P and S and what is their degree of relation?

Step‑by‑Step

1. Identify the direct links:

   • Q → P (parent → child)
   • Q → R (parent → child)
   • R → S (parent → child)

2. Draw the path from P to S:

   • P ← Q → R → S
     The path is:
     P → Q (1), Q → R (1), R → S (1). Total links = 3.

3. Determine the degree:

   • The longest path has 3 links → 3rd degree relation.

4. Identify the relation type:

   • P and S share a common ancestor Q but are not in the same direct line.
   • They are cousins: P is the uncle of S?
     Wait – check:
     Q is parent of P; Q is also parent of R; R is parent of S.
     So P is the uncle of S (P’s sibling R is S’s parent).
   • Uncle is a 3rd‑degree relation.

Answer:

• Relation: Uncle
• Degree: 3rd degree

Quick Diagram (text form)

   Q
  / \
 P   R
        \
         S

• P – child of Q
• R – child of Q (sibling of P)
• S – child of R (nephew/niece of P)

4. Quick Revision Summary