Father secretly sold our family land in Kerala, what actions can I take?

I recently discovered that my father sold our ancestral land in Kochi without consulting or informing me or my siblings. This land has been in our family for generations and was supposed to be shared among us. I am shocked and feel betrayed. He claims we have no say in this decision. I'm worried about losing my inheritance and want to know what legal steps I can take to challenge this sale or prevent further unauthorized transactions.