In a classic family relation riddle a person says that he has no brothers and no sisters and also says that the father of that man is the only son of his own father. How are the speaker and that man related respectively?

Introduction / Context:
This famous riddle about family relationships appears in many logical reasoning books. The original wording is often quoted as Brothers and sisters I have none but that man father is my father son. It checks whether you can translate a layered verbal description into a precise family tree. Solving it successfully requires careful tracking of who is being referred to in each phrase.

Given Data / Assumptions:
- The speaker is male and has no brothers and no sisters.- The speaker talks about a certain man, referred to as that man.- The speaker says that the father of that man is the only son of his own father.- If the speaker has no siblings then the only son of his father must be the speaker himself.

Concept / Approach:
The approach is to substitute expressions step by step. The key phrase is my father son. If the speaker is the only son of his father, then my father son refers to the speaker himself. Then you insert this understanding into the rest of the statement and identify that that man father must be the speaker. Once you know who is whose father, the relationship between the two men follows immediately.

Step-by-Step Solution:
Step 1: Because the speaker has no brothers and sisters, his father has only one son, namely the speaker.Step 2: Therefore the phrase my father son refers to the speaker himself.Step 3: The speaker says that man father is my father son. Replace my father son with the speaker.Step 4: After substitution the sentence means that man father is me. So the speaker is the father of that man.Step 5: Hence the relationship pair is that the speaker is the father and that man is his son. The correct description is father and son in that order.

Verification / Alternative check:
Draw a small family tree to verify. Place the father of the speaker at the top. The father has one son, the speaker. Below the speaker draw one more male figure, that man, and label the arrow from speaker to that man as father to son. Now confirm that the sentence that man father is my father son still holds. The father of that man is the speaker, and the only son of the speaker father is also the speaker, so the statement is self consistent.

Why Other Options Are Wrong:
Option B brothers would mean that the two men have the same parents. This cannot be true because the speaker has no brothers at all.Option C son and father reverses the order of the pair, but the question asks first for the relation of the speaker and then for the relation of that man, so son and father does not match the required order.Option D nephews is incorrect because that man is not a nephew of the speaker father but directly the son of the speaker.

Common Pitfalls:
Many learners get confused by pronouns and end up thinking that that man is the speaker himself reflected in a mirror. Others forget that having no brothers or sisters forces the phrase my father son to point back to the speaker uniquely. Writing down short labels such as S for speaker and M for that man and then translating the sentence in symbolic steps can greatly reduce confusion.

Final Answer:
The speaker is the father and that man is his son, so the relationship is father and son.