Uncle trying to sell the entire Property. What can I do to stop him ?

my grand father had four childerns 1.my father 2.my fathers brother 2.my fathers first sister 3.my fathers 2nd sister below details: 1.total property (land):24bigha approx 2.1.5bhigha my grandfathers self accaquiresd remaining parental. 3.my fathers brother sold 4.5bhigha in 2012,2bhigha in 2014 and 2 bhigha in 2015 after my fathers death in 2011 he is planning to sold all property with the help of grand father. 4.my fathers 2 sisters are little bit supporting him and not involved in this matter. questions below: 1.what to do to stop him doing that. 2.how can we get the share