so far, we have:
there are 5 siblings
there is a 50 acre parcel held as TIC
apparently there is 1 sibling that wants the land to be divided and he take some specific portion
none of you have to relinquish anything if you choose not to. Anybody can sue to partition the property through the courts if you choose. If the parties cannot come to an agreed upon division, the land will be sold at auction and the proceeds divided among the parties, after all expenses are taken out of course.
If you all can agree to some division of the property, then you head to the lawyers office to have everything documented properly.