New GST Registration.

Can someone help me with proof of residence as demanded during GST registration? Our house's electricity bill is in the name of my grandfather who passed away last year. And all tha related documents of property are still on his name. I'm trying to getting registration with my PAN.

Is there any other possible way to get this requirement completed?
And if rent agreement is the solution than isn't it necessary to have signature the my grandfather?

Please help.