Explanation
In this statement, Sita is talking about a man who is related to her in some way. According to the statement, the man is "the brother of the daughter of the wife of my husband."
Let's break down the relationships:
"The wife of my husband" refers to Sita herself.
"The daughter of the wife of my husband" refers to Sita's daughter.
"The brother of the daughter of the wife of my husband" refers to Sita's daughter's brother, who is also Sita's son.
Therefore, the man being referred to is Sita's son.