Please note this is a complicated question and I can only give you a general answer without additional information. You really need to speak with a probate attorney. If your dad had a will and left everything to your stepmother, then you will only have a life estate. However, if your dad died intestate (without a will) your stepmother would be entitled to her intestate share, which would be a set percentage of the Estate, plus $50,000. The children will also receive an intestate interest. This would include an interest in the home. If there is a will which left nothing to the spouse (stepmother), then she has what is called a right of election, which allows her to receive a certain portion of the Estate. There are several other issues that can arise in this scenario
You need to talk to an estate/real estate lawyer to sort this out. If the house was legally transferred to you a year ago subject to a life estate, your Stepmom has the right to continue living in the house, but can't require a re conveyance. When she occupies as a life tenant, she is obliged to pay the taxes and maintain the home. That's assuming of course that 34 years ago she in fact conveyed her interest in the house back to your Father.
Talk to a lawyer.
My answer to your question is for general purposes only and does not establish an attorney-client relationship,
You should contact an attorney in your area who works regularly with real estate and estates. Based on your description, it is difficult to ascertain which people possess which interests in the subject property. An updated abstract of title should show the relevant chain of title to the property, and that can be used to determine if "Stepmom" has any interest in the property.
This communication is intended only to provide general information. This communication does not create an attorney-client relationship.