Legal Question in Real Estate Law in Illinois

It appears you asked this and provided more information, which is helpful but insufficient. If sister's acreage was accessed from brother's prior to the split in title it may be that an easement was implied at the time title was split and father did not think that anything more formal was required. Therefore if brother is refusing to allow access there may be grounds for a court to declare an easement exists and if sister incurs costs to open new access the costs could be damages assessed against brother. This requires an attorney's involvement and can not adequately be assessed in this forum. What is unfortunate is the siblings' unexplained refusal to work out the issue amicably with each other.