Aryan has a brother named Bishnu. Aryan is the son of Chetan, and Dev is Chetan's father. In terms of relationship, how is Bishnu related to Dev?

Introduction / Context:
This is a simple generation-based blood relation question. You are given three generations: Dev at the top, his child Chetan and then Chetan's children Aryan and Bishnu. The task is to identify how Bishnu is connected to Dev. Such questions test your ability to track generations and recognise standard relationships like son, grandson, brother and cousin.

Given Data / Assumptions:
- Aryan has a brother named Bishnu. - Aryan is the son of Chetan. - Dev is Chetan's father. - Family structure is standard, with no adoptions or unusual relations.

Concept / Approach:
We can think in terms of generations. Dev is one generation above Chetan, and Chetan is one generation above Aryan and Bishnu. A person who is two generations below someone, and is the child of that person's child, is a grandson or granddaughter. Because Bishnu is a son of Dev's son Chetan, Bishnu is Dev's grandson. We only need to be careful not to confuse brother with cousin.

Step-by-Step Solution:
Step 1: Dev is the father of Chetan. Step 2: Aryan is the son of Chetan, so Aryan is Dev's grandson. Step 3: Aryan has a brother named Bishnu. Since Aryan and Bishnu are brothers, they share the same parents in this typical setting. Step 4: Therefore, Bishnu is also a child of Chetan. Step 5: Since Bishnu is the son of Chetan, and Chetan is the son of Dev, Bishnu is the grandson of Dev.

Verification / Alternative check:
Draw a simple three-level tree: Dev at the top, Chetan in the middle, and Aryan plus Bishnu at the bottom. The arrow from Dev to Chetan is father–son, and from Chetan to Aryan and Bishnu is father–sons. Any child at the bottom level is a grandchild of Dev. Since Bishnu appears at this bottom level as Chetan's son, his relationship to Dev is unambiguously grandson.

Why Other Options Are Wrong:
- Father: Bishnu is two generations below Dev, not above him. - Brother: A brother of Dev would share Dev's parents, not be a child of his son. - Cousin: Cousins are children of siblings, but Bishnu is directly from Dev's line. - Nephew: A nephew would be the child of Dev's sibling, not of Dev's own child.

Common Pitfalls:
Sometimes test-takers rush and see the word brother (Aryan's brother Bishnu) and mistakenly label Bishnu as Dev's brother as well. However, brother is a relationship within the same generation, while Dev clearly belongs two generations above Aryan and Bishnu. Always check how many generational steps separate two people; that usually narrows the relationship down to grandparent–grandchild, parent–child or sibling.

Final Answer:
Bishnu is Dev's grandson.