Overseas legal hership

Dear sir I am an independent housing loan service provider One of my customer (US citizen) is selling a property from USA florida,unfortunately the seller has expired and the spouse has obtained a death certificate and heirship affidavit from florida,but my legal lawyers are not accepting the affidavit,is there any other document to prove the legal heirship in US,or do i have get a legal heirship in india,pls help