Hello Raj. The sponsor can be a friend or relative. The sponsorship needs to be set up before the visa application is made. Your uncle needs to complete form INZ1025 - downloadable form
www.immigration.govt.nz. He has to prove that he has sufficient funds in his bank account. I sponsored a student while in NZ and I went to my bank and got them to print off a statement and sign it to say it was genuine. The sponsor needs to show sufficient funds for however long the visa is to be. So, $15,000 a year plus the money for the return flight. This money can stay in your uncle's account.