✅ Let's decode the statement step-by-step.

First, analyze "my mother's mother-in-law": Rishabh's mother's husband is Rishabh's father. Therefore, Rishabh's mother's mother-in-law is the mother of Rishabh's father, which means Rishabh's paternal grandmother.

The full statement now translates to: "Her mother's husband (who is the girl's father) is the only son of Rishabh's paternal grandmother."

If Rishabh's paternal grandmother has only one son, that son must definitively be Rishabh's father.

Thus, the girl's father is the same person as Rishabh's father. This implies that Rishabh and the girl share the same father, making them siblings.

Therefore, Rishabh is the girl's brother.

❌ Options B, C, and D are incorrect as the logical deduction establishes a sibling relationship, not a parental, avuncular, or cousin connection.

✅ To decode the relationship, let's break down the man's statement: "Her brother's son is my wife's brother-in-law's only nephew."

First, consider "my wife's brother-in-law's only nephew": The man's (M) wife (MW) has a brother-in-law. Given that "The man's sister is unmarried," this brother-in-law cannot be the man's sister's husband; thus, it must be the man's brother (let's call him MB).

MB's "only nephew" is the man's (M's) son (let's call him MSon).

So, the man's statement simplifies to "Her brother's son is M's son."

This implies that the woman's brother (WB) is the father of M's son, which means WB is the man's (M's) father.

Since the woman (W) is the sister of WB (who is M's father), the woman is M's Paternal Aunt.

❌ Options B, C, and D are incorrect as they do not align with the logical deductions from the complex blood relation riddle presented.

✅ Let's decode the relationship from the woman's statement: "my mother's father-in-law."

The woman's mother's father-in-law is the father of her mother's husband (who is the woman's father).

Thus, "my mother's father-in-law" refers to the woman's paternal grandfather.

The "only daughter-in-law of the woman's paternal grandfather" must be the wife of his only son, which is the woman's mother.

Since the man's mother is identified as the woman's mother, this establishes a sibling relationship between the man and the woman.

❌ Therefore, the man is the woman's brother, not her son, uncle, or cousin, as they share the same mother.

✅ Let's decode the statement step-by-step.

First, "Rohan's mother's only brother" refers to Rohan's maternal uncle.

Second, "The sister of my mother's only brother" (Rohan's maternal uncle) must be Rohan's mother herself, as the brother is stated to be "only".

Third, "Your husband's mother-in-law" refers to the woman's own mother.

Equating the two parts of the statement, Rohan's mother is the woman's mother.

Therefore, Rohan and the woman share the same mother, making them siblings.

Thus, the woman is Rohan's sister.

✅ Let the man be M and the woman be W.

✅ First, decode "Your mother's only brother's wife": W's mother's only brother is W's maternal uncle. The wife of W's maternal uncle is W's maternal aunt.

✅ Next, decode "my father's only daughter-in-law's mother": Since M is a man, his father's only daughter-in-law is M's wife (assuming M is the only married son or only son). Therefore, "my father's only daughter-in-law's mother" refers to M's wife's mother.

✅ Equating the two statements: W's maternal aunt is M's wife's mother.

✅ This implies that M's wife is the daughter of W's maternal aunt (and W's maternal uncle).

✅ The daughter of W's maternal uncle is W's cousin. Therefore, M is married to W's cousin, meaning the man (M) is W's cousin's husband.