Intestate and Locked Out

[jwest2007]

A couple of Issues:

My Mom died a few months ago without a well. She has a surviving spouse, who is not our father and he has no children. As I understand it, 50% of the real property they owned jointly will go to myself and my sisters. Currently, the older sister is acting like she owns the place and informed my younger sister she was not allowed to enter my Mom's house. Our stepfather concurred and told my little sister it was because of the "estate". First we'd even heard that one had been formed. Is this legal? We are inheritors jointly of a full 50% of the homestead of our Mother.

2nd Question, My older sister has begun to use a part of the adjoining property as a driveway to reach her travel trailer behind my mother's house. My mother did not wish my Grandmother's property to be used as a driveway and insisted that the drive be a continuation of her own driveway at the time the trailer was put in place. This adjoining property is now jointly owned by myself and sisters, with a 1/3 life estate to her husband as it was inherited property remaining solely in my mother's name. What can we do to stop her from making use of this property in this manner? Also, she has placed a storage building of some sort on the property as well. Essentially, she's acting like the whole place his hers. What can we do to establish our objections to what she is doing? The estate has been formed, but no action has yet been taken. Does my mother's husband, with his 1/3 life estate, have the right to do as he pleases with the property until he dies, are we subject to his wishes until that time?