Unless there is some sort of emergency, there is no reason to sell any property while the will is being contested. The authority of a power of attorney document ends once the person granting the power dies. Only the executor/personal representative of the estate has the power to sell a decedent's assets. However, if your step-brother's name is also on the title to the land, he may have authority under certain circumstances to sell the property.
Answered on May 15th, 2013 at 7:25 PM