If my mother has passed away and my step father is selling home, are my brother and I entitled to her half?

Maybe; very likely not. Most married couples in Oregon hold real property as "tenants by the entirety." This is a survivorship estate when one owner passes away, the other owner owns the whole of the property by operation of law. Check the deed by which your mother and step-father owned the property. Actually, too, if he's able to sell the house without probating your mother's estate, then it's almost certain they owned the house as tenants by the entirety.

The answer to this question depends on the language of the deed to the property. If your mother and your step-father had taken title to the property as ?husband and wife as tenants by the entirety, when your mother died your step-father became the sole owner of the property with no right of inheritance to you and/or your brother. If, on the other hand, they had taken title to the property as tenants in common, your step-father would be entitled to one-half the net proceeds of the sale and you and your brother would be entitled to inherit your mother's share, assuming she provided for that in her will. If she had no will when she passed, or if she did have a will but made no bequest to you and/or your brother, you need to talk with a lawyer about the process of filing a probate action to perfect your interests in the property.