New GST Registration - Query regarding documents

Don't make things look complicated in the eyes of GST officer..

Did you mean to say rental agreement has the name of "legal heir" of the owner of the property and the said agreement is very well registered stating the name of legal heir as "legal heir"?

If so, the rent agreement copy along with the declaration of legal heir can be submitted as supporting.

In whose name the business is? 

If possible make amendment in the rent agreement to include name of business owner, to the extent which may look simple to the GST officer to approve it without any queries.