In a family, Jasbir is married to Amrita, and they have one son, Ranveer. Amrita's brother, Karan, is married to Isha, and they have a daughter, Simran. Karan's sister-in-law on his father's side, Rhea, is married to Nikhil, and they have a son named Yuvraj and a daughter named Kavya. How is Rhea related to Amrita, and what is Ranveer's relationship to Kavya?
Respond very briefly.
Rhea is married to Nikhil, who is the brother of either Amrita or Karan since she is Karan's sister-in-law on his father's side. Given that Amrita and Karan are siblings, and Nikhil is married to Rhea, Rhea is Amrita's brother's wife, which makes her Amrita's sister-in-law and therefore Rhea is also Jasbir's sister-in-law by marriage. 

Ranveer is the son of Jasbir and Amrita, while Kavya is the daughter of Rhea and Nikhil. As Rhea is the sister-in-law of Amrita, her daughter Kavya would be Ranveer's first cousin, as their parents Amrita and Nikhil are siblings.