This unnamed man is the husband of Priya Koothrappali, Raj's sister.
He is indirectly mentioned in "The Allowance Evaporation" when Raj's father V. M. Koothrappali says to Raj "I have 6 children, 5 of whom are married and self-sufficient."
Trivia
- It's obvious that this individual would be a man since homosexual relationships are banned in India.