Amit is married to Sunita, and they have a son named Raj. Amit has one sibling, a sister named Priya. Priya is married to Arjun and they have two children, a daughter named Diya and a son named Nitin. Arjun's brother, Vijay, is married to Anjali. They have a daughter named Mira. Explain how Mira and Sunita are related, and describe Raj's relationship to Diya. Provide a very brief response.
Mira is the daughter of Anjali and Vijay. Vijay is the brother-in-law of Priya, who is Amit's sister. Since Amit is married to Sunita, Vijay is indirectly related to Sunita through marriage. Therefore, Mira is Sunita's niece through marriage, specifically, she is the daughter of Sunita's husband's sister's brother-in-law.

Raj is the son of Amit and Sunita. Diya is the daughter of Priya (Amit's sister) and her husband Arjun. This makes Diya, Amit and Sunita's niece. As a result, Raj and Diya are first cousins, as their respective parents are siblings.