Clear willed 2floors property Selling issue b/w brothers

Hi, Sir, Actually my Grand father made a clear registered Will in 1999 and Expired, which was his own independent self earned property, ie, 30*40 site, bangalore city central, which included ground floor, 1st floor and second floor, Where the will clearly says that his 3 sons should acquire the ownership of each floor which is mentioned by there name, So Sir, now my question is, ie,my father the eldest son is staying in 2nd floor house according to the will, & my father Really wants OR trying to sell his house from past 2years,which includes BBMP A khata in his name, But my father younger brother whos staying in 1st floor house according to will, is not allowing to sell, Hes abusing continuosly with bad words, and hes taken almost all the facilites in site, maximum towards his house, including water, parking place etc, & Hes taken out & kept all the orginal docs/papers of the site, in his home locker` Hes telling he will never allow my father to sell the property or our house & one more thing is actually my father 2nd younger brother whos staying in Ground floor was also Fully ready to sell his house intially, But now my fathers 1st floor younger brother has planned, blackmailed & finally influenced him also not to sell, by saying hime U will not good price even if U sell etc etc So Sir, how can my old father sell his house in the above situation, when his own younger brother only blocking him intensionally???