A man says to a lady, "Your mother's husband's sister is my mother." In this blood relation puzzle, how is the man related to the lady?

Introduction / Context:
This blood relation problem uses a layered phrase involving the mother and father of the lady and a sister of the father. The man identifies this woman as his own mother. Our goal is to determine how the man and the lady are related. Problems like this test careful reading of expressions such as your mother's husband's sister and the ability to translate them into a clear family tree.

Given Data / Assumptions:
• The lady has a mother.• The husband of the lady's mother is the lady's father.• The sister of this father is the lady's paternal aunt.• The man says this paternal aunt is his own mother.• Standard family structure is assumed with no hidden complexities.

Concept / Approach:
Your mother's husband is the father of the lady. The sister of that father is the lady's aunt on the father's side. When the man says that this aunt is his mother, he is saying that he is the child of the lady's paternal aunt. A child of one's aunt is a cousin. Therefore, the man is the cousin of the lady. This is the central insight that transforms the nested phrase into a simple cousin relationship.

Step-by-Step Solution:
Step 1: Let the lady's mother be M and her father be F.Step 2: The phrase your mother's husband points to F, the lady's father.Step 3: The sister of F is the lady's paternal aunt, call her A.Step 4: The man says that A is his mother.Step 5: If A is the man's mother, then the man is her child.Step 6: The lady is the child of F, who is the brother of A.Step 7: Children of a brother and a sister are first cousins, so the man and the lady are cousins.

Verification / Alternative check:
We can draw a small family tree with grandparents at the top and their two children F and A beneath them. F has the lady as his child, and A has the man as her child. The lady and the man therefore share the same grandparents and are in the same generation. This is precisely the structure of first cousins. There is no information in the question that suggests any other relationship such as sibling or nephew would be more appropriate.

Why Other Options Are Wrong:
Brother of the lady: For this to be true, the man and the lady would need to share the same parents; instead they share grandparents.Son of the lady: This would place the man in a younger generation, contradicting the role of his mother as the aunt of the lady.Nephew of the lady: A nephew is child of one's sibling, but the man is child of the lady's aunt, not her sibling.Uncle of the lady: An uncle would be a sibling of her parent, not the child of that sibling.

Common Pitfalls:
Some candidates misread your mother's husband's sister as somehow pointing back to the lady herself, which leads to confusion. It is important to break the phrase into steps and to recognise that the final woman identified is the paternal aunt of the lady. From there, the idea that the man is the child of this aunt quickly leads to the correct cousin relationship.

Final Answer:
The man is the cousin of the lady.