Since you were born in India apply to magistrate for issue of your birth certificate 

2) you can apply on basis your leaving certificate 2)affidavit of your mothers stating  your birth date and year 3) your family ration card 4) your photo.

3) you are eligible for OCI card as your father was Indian citizen 

4) you can obtain father school leaving certificate to prove he was Indian citizen 

5) if your parents owned any  land in India land records would help in proving that  they were Indian citizens 

Yes you can apply on above grounds

If you do not have an Indian passport but you are applying on the basis that your parents and/or grandparents were Indian citizens, copies of the following documents are required:
Proof of both parents current citizenship and previous citizenship.
Your birth certificate that mentioned your parents' name. If you are applying on the basis of your grandparents being Indian citizens, your birth certificate as well as your parent's birth certificate. All birth certificate must show the parent's names clearly so that to establish the relationship with your parents and grandparents.

i suggest you check the Nepali rules rather than Indian rules for OCI application

you already have your dad registered as a nepali citizen

so on that basis you can check the rules prevalent in Nepal 

My uncle is an indian citizen , could he help me in this process ? 


* My grand Father's brother is still alive , could he help in this process ? 

Ask them to prepare family tree and gather documentary proof where it can shown that your father and uncle are siblings and great grand father`s legal heir certificate.

1. You do not have the appropriate documents required for claiming OCI Card.

2. However, you can apply by submitting your father's education certificate received from indian School/Board.

Dear sir 

Your case is very complicated as you have no proof of citizenship of India. 

But the way you can get the proof is that if some how you can get the record of your birth from the hospital where your mother gave birth to you. It can be of great help to you. 

As they enter the birth of every child along with mother and father name in the register on basis of this you can apply for Birth certificate in India in office of Sub registrar birth and death of the area where you were born. 

Ask your relative to some how get these details from the hospital of your birth. 

Regards

Mohit Kapoor

You can prove your mother relationship by educational certificates wherein you may find your mother's name;

you may also birth certificate in which your mother's name shall be found;

The relationship between your father and his brother can be established  through their father, if that is possible then you may proceed.

You may look for any document that is admissible for getting OCI status

You can still get the birth certificate of your father or grandfather for which you will have to file in application with the SDM for delayed birth registration order. After that, birth certificate can be procured after  documentation is done with the department of birth and death.

once you get the birth certificate of your father or grandfather getting OCI card would be very easy.

Your uncle's or other relatives cannot help in getting the OCI card. Also, your mother can apply for her birth certificate if she was born in India.