E is the son of A, D is the son of B. E is married to C. C is B's daughter. How is D related to E?

Let's break down the relationships step by step:

• E is the son of A.
• D is the son of B.
• E is married to C.
• C is B's daughter.

So, C (E's wife) is the daughter of B.
D is the son of B.

That means C and D are siblings (brother and sister).

Since E is married to C, and D is C's brother, D is E's brother-in-law.