A and B are walking togather.A's daughter's daughter C is B's father's daughter-in-law's husband's child.what is the relation of B with C.

Working through the relationship: C is A's daughter's daughter (A's granddaughter). C is also B's father's daughter-in-law's husband's child, which means C's mother is married to B's father's son (B's brother). This makes C B's niece. But since B's father's daughter-in-law could be B's own wife, and the husband's child would then be B's child. Let me reconsider: B's father's daughter-in-law = B's wife, husband = B, child = B's child. So C is B's child, making B the father.