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 toward a person in a photograph, Anjali said "He is the only son of the father of my sister's brother."
How is that person related to Anjali ?
The relations may be analysed as follows :
Sister's brother -- Brother;
Brother's father -- Father;
Father's son -- Brother.
So, the person in the photograph is Anjali's brother.
Hence, the answer is (e).