We start by analyzing the sibling relationships:
This establishes that Rajat, Garima, and Harish are siblings.
Next, we look at the connections involving Harish and Jyoti:
From this, Harish is the father of Karan's wife. Hence, Harish is Karan's father-in-law.
Finally, we determine Rajat's relationship to Karan:
Therefore, Rajat, as the brother of Karan's father-in-law, is the wife's father's brother.