A is the father of C and D is the son of B. E is the brother of A. If C is the sister of D, how is B related to E?

Introduction / Context:

This blood-relation puzzle links five people—A, B, C, D and E—and asks how B is related to E. The information includes father–child relationships, a brother relationship and a sibling relation between C and D. The question ultimately targets an in-law relation (“sister-in-law”), a common theme in such reasoning problems.

Given Data / Assumptions:

• A is the father of C, so A is male and C is A's child.
• D is the son of B, so D is male and B is a parent (gender not yet specified).
• E is the brother of A, so E is male and a sibling of A.
• C is the sister of D, so C and D are siblings, and C is female.
• We assume siblings share the same pair of parents unless mentioned otherwise.

Concept / Approach:

We know that C and D are siblings, and that A is the father of C while B is a parent of D. To make them siblings in the usual sense, A and B must be the two parents of both C and D. Once we recognise A and B as a married couple, the connection between B and E (who is A's brother) becomes a typical in-law relationship: B is E's sister-in-law.

Step-by-Step Solution:

Verification / Alternative check:

We can assign sample roles to verify. Let A and B be a married couple. They have two children: C (female) and D (male). E is A's brother. C is the sister of D, as given. D is B's son, and C is A's daughter. In this picture, from E's viewpoint, his brother's wife B is his sister-in-law. All given relations hold and the conclusion is consistent.

Why Other Options Are Wrong:

“Daughter” would mean B is a child of E, which contradicts the generational information—E and A are brothers, while B is in A's generation, not a generation below.

“Brother” would require B to be male and a sibling of E, whereas B is positioned as the partner of A, not as A's sibling.

“Husband” would imply B is male and married to E, which does not follow from any given data.

Common Pitfalls:

Some students overlook that C and D being siblings, combined with “A is father of C” and “D is son of B”, almost forces A and B to be their parents together. Recognising that standard assumption is crucial to discovering the in-law relation. Drawing a simple family diagram can greatly reduce confusion.

Final Answer:

B is related to E as his sister-in-law.