Classification (family relations – role type): Three terms denote sibling/extended relations; one denotes a direct parent. Identify the odd one out.

Introduction / Context:
Family-term classification often hinges on role type. Brother and cousin are lateral relations (sibling/extended), and nephew is a next-generation collateral relation. Mother, however, is an ascendant (direct parent). The split between lateral/collateral kin and direct ascendant establishes a crisp odd-one-out criterion familiar from basic reasoning tests.

Given Data / Assumptions:

• Brother → sibling (same generation).
• Cousin → extended lateral relation (same generation across branches).
• Nephew → collateral next generation (child of sibling).
• Mother → direct ascendant (parent).

Concept / Approach:
Group by genealogical direction: lateral/collateral versus ascendant. The only ascendant in the list is mother, so that term becomes the outlier while the remaining three can be grouped as non-ascendant relatives.

Step-by-Step Solution:

Verification / Alternative check:
Check dependency language: “child of” applies only to mother among the options; the others depend on sibling/extended links.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing “nephew” with “son.” Nephew is the child of a sibling, not a direct descendant.

Final Answer:
Mother