Miss guide grandmother to take over the property

Hi, i have 5 brothers and one sister. we have some property. sister got married. and rest 6 of us used to stay in a one home. elder 3 brothrs deside to make thr own house and leave thr parents home and desided to give the property to rest 3 younger brothrs. they only can stay over thr but cant sell out the property. if the do so then eithr they have to take permission from othr 3 brothers and one sister, and then sell it or else after makeing the sale of the property all will be equally devided into 7 member. with this clause 2 brothers signed in the agreement and one brothr didnot signed and sis also. now one of them made a false agreement and provogue to my mom to signed that paper. so that only 3 brothrs can have all the property equally. rest 4 of us dont knw about tht property and didnt even signed. now they are selling it with out informing us. can we claim the share of the parents property or we dont have any chance to get the share. if we can then what action should we take for the same. please advice.