Grandfather did not make will how will division be done among children

Sir my mother is having 4 sisters and 2 brothers and one younger brother is a step one so now my grandfather is no more died in 2011 and he dosnt created any will on behalf of any one so now what to do in this case if 1 of them is not agree to sign agaist to register the case in court against propert and step brother of my mother is going to sell the house with the help 1 of my mother sister sir plzz let me know how to get rid of it wht should my mother do to take her fathers property contributation how she can take her part....