Bank Mortgaged property sold without the knowledge of the Bank

Hi Sir. 1. On 2006 my father and his brother partitioned their parental property. With out the consult of their Son and daughters who are major at that time. 2. On 2007 Both the partitioned property has been registered to bank for educational loan.. .. 3.On 2008 my father's brother threatened and forced to sell his part of the land which he gave as collateral to bank. To local money lender for a meager price.. . With out their daughter s consent.. but they are aged 17 and 15 at the time of sale deed. 4.On 2009 the person who got the property cut down 3 well grown tamerine tree at the property. Without the knowledge of the bank and property owner. 5.Now the collateral property is under debt recovery tribunal due to non payment of loan amount.. 6.Now bank is forcing me to pay the loan amount. Without fail. 7.And the land buyer had not settled full amount to my father's brother.. 8.Since my sister's are to be married. And we have no funds left. If we get back the property . Atleast it will be useful for their marriage expenses. Kindly guide on this regard..