Not having legal documents for adoption

Hello Sir/Ma'am, I am having confusion for making a passport. I am 24 years old. My father passed away when I was 1 year old. I have been living with my maternal uncle and aunt since then in Ankleshwar,Gujarat. My mother lives in Nashik,Maharashtra. My maternal uncle and aunt has been taking care of me since then. I have studied in Ankleshwar. My aadhar card and all documents are based on the address of Ankleshwar. My all the documents contain my actual father's name as father's name. No formal adoption process has been carried out. Now while filling up passport application, there is a column where you have to enter father's name., mother's name, legal guardian's name. Can I add maternal uncle's name as legal guardian's name. And if I can add, what are the documents required for the same. Is adding my maternal uncle's name as legal guardian will be helpful for getting visa for my uncle and aunt in future like after 2-3 years if they wish to come and stay with me for longer period(5-6 months).