All six members of a family A, B, C, D, E and F are travelling together. B is the son of C but C is not the mother of B. A and C are a married couple. E is the brother of C. D is the daughter of A. F is the brother of B. How is E related to D?

Introduction / Context:
This question describes a six member family and asks you to identify how one member, E, is related to another member, D. The key is to place everyone correctly into generations using clues about sons, daughters, brothers and the married couple A and C.

Given Data / Assumptions:

• Family members: A, B, C, D, E and F.
• B is the son of C, but C is not the mother of B.
• A and C are a married couple.
• E is the brother of C.
• D is the daughter of A.
• F is the brother of B.
• We assume A and C form a standard husband and wife pair and that children of a couple have both of them as parents.

Concept / Approach:
The phrase "B is the son of C, but C is not the mother of B" tells us that C is male and must be the father of B. Since A and C are a married couple, A becomes the mother in the pair. Then, since D is the daughter of A, D is also a child of C. Once that is clear, E, who is the brother of C, lies one generation above D, making E an uncle of D.

Step-by-Step Solution:
Step 1: From "B is the son of C, but C is not the mother of B", we conclude that C is a parent of B but not female, so C is the father of B.Step 2: A and C are a married couple. If C is the husband and father, then A is the wife and mother in the family.Step 3: D is the daughter of A. Since A and C are married, D is also the daughter of C. Thus B and D are siblings, children of A and C.Step 4: E is the brother of C. This means E is in the same generation as C and is another child of C parents.Step 5: Since C is the father of D, and E is C brother, E is an uncle of D.Step 6: The question asks, "How is E related to D?" The correct relationship is uncle.

Verification / Alternative check:
We can sketch the family tree. Put A and C in the parent generation as a married couple. Their children are B (son) and D (daughter). E is the brother of C, so E belongs to the same generation as A and C, not the children generation. F is the brother of B and thus another child of A and C. Looking at D, her father is C, and E is C brother, so E is clearly D paternal uncle.

Why Other Options Are Wrong:
E is not the father of D, because the father role is filled by C. E is not the brother of D, because he is in the parent generation, not in the children generation. E is not the grandfather of D, because there is no suggestion that he is the father of A or C. The relationship is fully determined and does not remain ambiguous, so "cannot be determined" is also incorrect.

Common Pitfalls:
A common error is to misread the line "C is not the mother of B" and assume that C might be an aunt or some other relative. In fact, that line is explicitly there to force you to recognise C as the father. Another mistake is to treat E as a sibling of B or D instead of correctly placing him as a sibling of C. Carefully distinguishing generations is crucial to solving such problems reliably.

Final Answer:
E is related to D as an uncle.