In this blood relation question, Kailash points to an old man and says, "His son is my son's uncle." Based on this statement, how is the old man related to Kailash?

Introduction / Context:
The question presents a classic blood relation scenario where a single sentence connects three different people. Kailash describes an old man and the old man's son in relation to his own son. We must use this information to find the relationship between the old man and Kailash. Such problems test the ability to decode phrases like my son's uncle and to distinguish between paternal and maternal uncles.

Given Data / Assumptions:
• Kailash points to an old man.• He says, "His son is my son's uncle."• An uncle of a child is either the brother of the child's father (paternal uncle) or the brother of the child's mother (maternal uncle).• Standard exam convention assumes the uncle mentioned in this kind of question is the paternal uncle unless there is specific information about the mother.

Concept / Approach:
We interpret my son's uncle as Kailash's brother in the usual exam setting. If the old man's son is Kailash's brother, then they share the same father. Therefore the old man must be Kailash's father. The key to solving the question is recognizing which person is positioned one generation above both Kailash and the old man's son and then matching that role with the description of the old man.

Step-by-Step Solution:
Step 1: Let the old man be X and his son be Y.Step 2: Kailash says that Y is his son's uncle.Step 3: In standard reasoning questions, my son's uncle is usually my brother, that is, the brother of the child's father.Step 4: So Y can be taken as Kailash's brother.Step 5: If Y is Kailash's brother, both Y and Kailash must be sons of the same father.Step 6: The father of Y is the old man X. Hence the old man X is also the father of Kailash.

Verification / Alternative Check:
Visualise a simple family: an old man with two sons. One son is Kailash, and the other is Y. Kailash has a son. The other son Y is then the paternal uncle of Kailash's child. This perfectly matches the statement his son is my son's uncle. No other role of the old man can satisfy this description as cleanly in the standard exam interpretation.

Why Other Options Are Wrong:
Grandfather of Kailash: If the old man were Kailash's grandfather, the old man's son would be Kailash's father, not his brother, and the description would not match.Father in law of Kailash: In that case, the old man's son would be Kailash's wife, which is impossible.Uncle of Kailash: If the old man were Kailash's uncle, then his son would be Kailash's cousin, not his son's uncle in the standard sense.Relationship cannot be determined: The information is clear enough to establish that the old man is Kailash's father under standard assumptions.

Common Pitfalls:
Many candidates overcomplicate the problem by considering both maternal and paternal uncles simultaneously and then feel that the relation cannot be determined. However, exam questions normally assume the paternal side unless explicitly told otherwise. Another mistake is to treat the old man as Kailash's grandfather instead of his father, which breaks the relationship described in the statement.

Final Answer:
The old man is the father of Kailash.