Explanation:

- The girl in the photograph is described as Raghav’s father's mother’s daughter’s only brother’s daughter.

- Break it down:

- Raghav's father's mother is Raghav's grandmother.

- Grandmother's daughter is Raghav's aunt (his father's sister).

- Her only brother refers to Raghav's father.

- Raghav's father's daughter is his sister (the girl in the photograph).

- Thus, Raghav's father is the girl's father.

- The relationship of Raghav’s father to that girl’s mother in the photograph is Option:3, Husband.