In decipher jumbled up description type of questions, a round-about description is given in the form of certain small relationships and direct relationship between the persons concerned is to be deciphered.
Pointing to a photograph, Vipul said, "She is the daughter of my grandfather's only son." How is Vipul related to the girl in the photograph ?
My grandfather's only son -- My father.
So, the girl is the daughter of Vipul's father i.e., Vipul is the girl`s brother.