Brother sold our family house in Chennai without my knowledge?

I am devastated. My elder brother sold our ancestral house in Chennai where we both have equal ownership. I wasn't informed or consulted at all, and now he's not answering my calls. This property was left to us by our parents and held immense sentimental value. I feel betrayed and unsure what legal steps I can take to challenge this sale. Is there a way to potentially reverse the transaction and claim my share?