I want to purchase the one Acre of property deeded to 5 brothers and sisters (including me) upon my fathers death in 2011. Brother won't cooperate.

Deed to 1 acre of property fell to 5 brothers and sisters after the death of my father in 2011. All, but 1 (my brother) agree to sell their part to me for $15,000 each. I have, single-handedly, paid the taxes and maintained the property since my father's death in 2011. Unfortunately, my brother can be difficult to deal with and wants more money. The property in question adjoins my own property and has been valued at $80,000. I have a copy of the current Deed listing my father's name and all names the property falls to upon my father's death. A copy is also on file at the courthouse. How can I get my brother to cooperate? My father died in 2011 leaving the Acre of property adjoining mine to his 5 children. My brother will not cooperate but he has yet to file any paperwork that I know of.