Since you and your father were born in Shillong , but you are Malayali by origin , you will need specific documents to prove Kerala nativity , as per Kerala government norms .

Required documents:

• Father's/ancestor’s Kerala school certificate or ration card

• Community certificate (OBC) from Kerala

• Affidavit declaring you are Malayali by origin

Kerala Nativity Certificate: https://www.careers360.com/articles/kerala-nativity-certificate