My father gifted our family property to his second wife without informing us?

I'm from Pune. Recently, I found out that my father has gifted our ancestral property to his second wife without informing me or my siblings. We have been living in this house for over 20 years. Is it legal for him to do this without our consent? We feel betrayed and are unsure of what actions we can take. Can this gift deed be challenged in court? What are our rights under Indian property laws?