Blood Relations — Study Notes

Overview

Blood Relations is a staple of logical reasoning in competitive exams, including the SOF NSO. The topic tests your ability to decode family relationships described in words or pointing statements and translate them into a clear family tree. You'll be asked to identify how person A is related to person B after a chain of relationships is given, or determine the gender and exact relationship of a hidden person.

In the NSO, 1–2 questions typically appear from this topic, often mixed with verbal or analytical reasoning. Mastery requires two skills: understanding the vocabulary of relationships (uncle, maternal grandmother, sister-in-law, etc.) and quickly building a mental or rough diagram of the family tree. Most mistakes come from confusing paternal and maternal sides or misjudging gender from ambiguous descriptions. With practice, these become quick 30-second solvers.

The problems come in two main formats: **family-tree style** (A is the son of B, B is the sister of C — how is A related to C?) and **pointing-style** (A points to B and says "Her mother is my mother's daughter" — who is B to A?). Both require systematic step-by-step decoding. Let's break down the essentials.

Key Concepts

• **Generation levels matter.** Always track whether people are in the same generation (siblings, cousins), one generation apart (parent-child), or two apart (grandparent-grandchild). Mixing generations is the fastest route to wrong answers.
• **Gender is critical.** Many relationships change meaning with gender: brother vs sister, uncle vs aunt, grandson vs granddaughter. If gender is not stated, consider both possibilities or look for clues in pronouns (he/she, his/her).
• **Paternal vs maternal side.** Uncle can mean father's brother or mother's brother. Aunt can be father's sister or mother's sister. The prefix "maternal" or "paternal" clarifies, but if omitted, check the problem context.
• **Spouse links connect families.** If A is married to B, then A's parents become B's in-laws, and B's siblings become A's brothers/sisters-in-law. Keep track of marriages to avoid dead ends.
• **Use symbols or abbreviations.** In rough work, draw circles for females, squares or triangles for males, and use lines to show parent-child or marriage links. Or use letters with +/- or M/F labels. Speed comes from a consistent notation system.
• **Only-child and sibling clues.** "Only son" or "only daughter" means no other children of that gender in the family. This narrows possibilities sharply in complex puzzles.
• **"My mother's daughter" = me or my sister.** In pointing problems, always simplify possessive chains step by step. "My mother's daughter" is either the speaker or the speaker's sister, never the mother herself.
• **Count carefully in multi-step chains.** If A is the father of B, and B is the father of C, then A is the grandfather of C — two generations up. Track each link to avoid off-by-one errors.