my widowed mother try to sell a property,but i don't trust proper

hi,i m living in delhi with my family on rent,but there is a property of my expired father who died in 2008 ,my mother tried to sell that property by a local dealer,they said to her that they will sell it and until then the property should be given to rent,after some time they informed that they are selling it but said they have to keep property papers with them,and my mom gave them.after couple of days they gave some couple of lakh and said they will give the rest later.till now they have given only 10 lakh and are not giving the rest of money. i think they are cheating with my family me and my brothers are the nominees, my DOB is 3/11/1996,my real brothers are aged (big brother)12/8/1993 & (small brother) 23/11/1997 property was sold in 30 lakh but now it cost 1 cr. WE WANT THAT PROPERTY BACK .is their any hope,pls help in my view i think they are going to wait until my small brother lose the title of underage and then they will make their move.they have our property papers my mother had not yet signed any legal paper nowdays law can be manipulate i know,and i think they can harm us if we dont like to sell property