"Raj's grandfather is old."

Translation: राज के दादा बूढ़े हैं।

[Vivek_Orton]

Why it is not "Raj kaa dada"?

[vinay92]

दादा is treated as plural as a show of respect.

[Rebekah326836]

It is Raj ke dada as dada is an older person so ke is put instead ka to show respect