When you say “divided” was this by individual deeds with legal descriptions or in some other manner? If it was, it is easy to determine what your grandmother later sold. However, say it was by inheritance - I give X to my five children. If this was the case, and the land was not divided and then transfer during probate, then you have a co-tenancy issue of some type.
So the issue is, how was the land transferred to your grandmother and the four others?