1. Mayank once told that he used play with his dadi.
2. As per Shilpa aunty Mayak Dad is dead. But there might some mishap happened in the past hence the conclusion.
3. Not the least, all these rules out if Mayank and Adhiraj dont carry the same surname.
Finally I think that Mayank's family will reunite again.
But personally I want that Nupur's family should accept Mayank as "he is" not b'coz he is Adhiraj's brother. We all know that Mayank is a wonderful character and Nupur's family should understand that.