Explanation

If A is the father of C and C is the sister of D, then A is also the father of D; since D is the son of B, this means B is the wife of A, making B the sister-in-law of E (A's brother). 

Explanation:

A is the father of C and D are siblings. 

D is the son of B. 

Therefore, B is the mother of D and the wife of A. 

Since E is the brother of A, B becomes E's sister-in-law.