The answer to the riddle is your sister, but the wording can be confusing at first. The key is to carefully follow each family connection in the sentence:

“I am your wife’s mother-in-law’s daughter.” Once you break it down step by step, the relationship becomes much easier to understand. First, we need to identify who your wife’s mother-in-law is.

Your wife’s mother-in-law is your mother, because your mother is the mother of the person your wife married — you. So the first part of the riddle means: your wife’s mother-in-law = your mother. Next, the riddle says the person is your mother’s daughter.

Your mother’s daughter would normally be your sister, because she is the daughter of the same woman who is your mother. Therefore, the person describing herself in the riddle is your sister. There is one small twist, though: if the person being asked the riddle is a woman, the answer could technically be herself, because she is also her own mother’s daughter. However, in the traditional version of this riddle, the expected answer is your sister. The trick is simply following the family connections carefully: wife → mother-in-law → mother → daughter.