A man said to a lady, “Your mother's husband's sister is my aunt.” How is the…

Answer: Sister.

Explanation:

• Your mother's husband = your father (assuming the usual interpretation).

• Your father's sister = your aunt (the lady's paternal aunt).

• The man says this same woman is his aunt, so she is also a sibling of the man's parent.

• Therefore the man's parent and the lady's father are the same person, which means the man and the lady share a parent and are siblings.

Note: This explanation follows the standard interpretation that "your mother's husband" refers to the lady's father.