Brother took a loan using our property as collateral without telling me?

I'm from Pune and I just discovered that my brother took a personal loan and used our jointly owned property as collateral. He never informed me and now there is a notice from the bank threatening to auction the property if the loan isn't repaid. I feel betrayed and scared as this is our ancestral home. What legal action can I take to protect my share of the property and hold him accountable?