This is a paternal relation where the person can indicate to photographs or just do a verbal communication.
Pointing out to a photograph, a man tells his friend, ‘She is the daughter of the only son of my father’s wife’. How is the girl related to the man in the photograph?
As the man said, he is the only son of his Mother.
And the girl in the photograph is the daughter of the only son of his Mother.
So, the girl in the photograph is daughter of the man.
Pointing to a man on the stage, Rashi said ‘He is the brother of the daughter of the wife of my husband’. How is the man on the stage related to Rashi?
According to Rashi’s conversation, that man is the brother of her daughter.
So, it means that man is son of Rashi.