To sell out my share of property

Dear Sir / Madam We own a house in mumbai which was purchased by 4 brothers together but in the name of third brother way back in 1962 sale deed / conveyance deed is avl. but unfortunately the third brother expired in 1970 her widow got remarried to his younger brother in 1972 and again got widow as time passed all brothers expired only widow of 2 brothers are left out, Third brothers wife and my mother the 2nd in row, we all were staying together till date now due to internal family disputes we have taken by ourselves 1/2 portions occupied by us under our control but on paper it is still in the name of youngest brother her wife who was remarried to his another brother and again got widow refuses to give us our share or sign any documents pls advice All the children from all the 4 brothers are married and are away only one daughter from 4th brother to 3rd brothers wife is unmarried and is staying with her mom in another 1/2 portion occupied by them how can i get my legal rights and how can i sell my share of portion as i dont want to stay there to avoid unnecessary daily disputes pl note i am 49 unmarried sister is 44 my mom is 79 and my chachi or widow of 3rd & 4th brother to my father is 77 Request for your guidelines