Estate Law Questions? Ask an Estate Lawyer.
If the property was in the name of his spouse and they were legally married, then under Mississippi law if she died without a will, 50% of the property was inherited by her spouse and 50% of the property was inherited by any child or children that she had (there must be legal adoption papers on record or a birth record, otherwise it does not matter if she "raised" this woman -- if she is not a biological or adopted child, she cannot inherit anything). If this woman is not biological or adopted daughter of his spouse then 100% of the property would pass to your father. Once your father passed away, his portion of the property, whether it is 50% or 100% passes to his own biological children. My suggestion to you at this point is to have a lawyer draw up a letter to this woman to determine what her relationship was to your father's spouse. If there is no birth record or adoption record then you are legally within your rights to evict her from the property and claim the estate for your father's children. If she is a legitimate heir then something must be worked out with her where she pays a 50% rent for living there (to be split among your father's children) or for the property to be sold and split between her and your father's children.