Under RTI Act 2005 Public Information Officer Has Refused To Give Information To Blood Related Family Member As A Third Party. Without Official Subdivision Of Inherited Property How Does Blood Related Legal Heirs Becomes Third Party?

This sounds like a legal matter in India, perhaps? You are asking on a world site.
I am in the US, and have no idea what the answer is for another country, but I am guessing that there is a restricted definition of the term blood relative. Often it means 'immediate family,' and that means children, parents, and siblings only. It might be extended to aunts/uncles/nieces/nephews.

You should be able to find the definition on your area's web page.

It would be up to the lawful authority in your jurisdiction to give you a formal standing as a third party of an inheritance and is unlikely to happen in my opinion. You should consult with your own counsellor to get official clarity in this matter.