Regarding Medical Admission

My father migrated from Andhra Pradesh to Chennai, Tamil Nadu. He did his M.TECH at IIT Madras. He settled thereafter in Chennai for the next 23 years.He married a Telugu Brahmin girl but my mother is born and brought up in TamilNadu.We belong to the Adi-Andhra community. Based on my father's community certificate and his T.C, he got myself and my sister community certificates in TamilNadu as Adi Andhra. Now my sister wrote the NEET exam and applied for the TamilNadu state medical counselling. They released the merit list and listed my sister's name as OC. Now when consulted , they told us that my father's A.P community certificate as the reason to list in O.C. Is the Medical counselling justified in doing that. Please help me honourable lawyers!!!!