Property dispute..

Hi sir. After the death of my father my brother and sister asked mom to divide the property as my dad has not left any will.. * my dad had 2 marriage n my mom is the second n legal wife,as the first .marriage ended in a divorce.. my bro n sis belong to the first marriage.* so after the continued pressure my mom agreed to divide the property. I was may b 20 yr old then. N my mom is not that educated.. so only on the basis of trust she signed on the notary papers. Bt later it turned out my sis and bro has taken 75 % of the property ,n got us ,tricked us to sign that paper.. now as soon as the property papers were signed my bro brought his divorced mother into the house n forced us to leave the house n live in our area of the property .. when we protest they come to beat us- ( me and mom.) Thy did not give equal share of property to us as it was divided into 3 parts.. 1 for sis..1 for him.. and 1 for me and mom both, where it should have been divided into 4 equal parts.. my mom being the legal wife of my dad, v r facing such injustice everyday they taunt us,say bad languages to my mom n me,.. and v could not do anything bcz we have signed the notary papers. I want to know sir/mam what can we do.. to teach him a lesson.. does my mom has the right to change the will again??? And divide everything equally. And do my brother have the right to bring his mom here in my dad's house when c was divorced already.. .? What kind of actions can we take.. ? Please help us we really need help..