Adopted son with no real documentation to prove have been adopted

Hi All, I have been adopted by the elder sister of my biological Father, Although I have been brought up by aunt like her own kid, since I was less than a year old. They haven't completed any formalities that could prove that am their adopted son. But I have my adopted parents name on all the marks cards(SSLC, 2nd PUC, Engineering) as well as on the birth certificate as my parents. After completing my education, Birth certificate was newly registered based on SSLC marks card, as I never had one before. Unfortunately, both of my adopted parents passed away very recently. So I guess I can't complete any of the formalities on my own. Though am the only boy kid for both the families, I have no idea, if am the legal heir of neither of the families. The question is, am I the legal heir of my adopted parents or that of my biological parents? As I have nothing else to prove that either of them are my parents. It seems to be like I am on no man's land. I have heard that both families are dealing with property settlement without even informing me. And for the worse, after my adopted father died, they have already sold a bit of land among themselves without even informing me or my adopted mother(as she happens to be the second wife of my adopted father, as he remarried once his first wife passed away). Please advice if I'd get my share as a legal son of my adopted parents. In fact, even if I don't stand a chance, I would retain my adopted parents as my real parents all my life, as they are the ones who have gifted me the life that am leading. Regards, Chidananda