If your birth certificate, school leaving certificate passport etc does not reflect your biological father name and you don't have any documentary evidence you would not be granted OCI

1. You can produce the copy of their marriage certificate.

2.You can produce the copy of your birth certificate.

On these two documents you can apply for OCI card in India.

What is the basis and source that makes you claim to have been born to a NRI who was your biological father ?

Based on the source you may make a search for the details of your biological father and look for the possibilities to get OCI.

You have to work hard to gather the details of your father.

1. You are a citizen of USA and not India.

2. You can not have a certificate of Non Resident Indian since you are not an Indian at all by birth.

3. You also can have the Overseas Citizen of India card since one of your parents is an Indian..

4. For changing the name of your father, your mother shall have to execute under affidavit that she has not mention her new husband's name in your required birth papers which she wants to correct now in the USA.

5. In India, your father shall have to execute an affidavit before a first class judicial magistrate in India affirming that he is your biological father as per the records of the hospital where you were born and inadvertently, your step father's name has been mentioned in all your birth documents which is required to be corrected now.

6. With the help of this affidavit, you can apply for the OCI certificate in India.