In legal matters, it's essential to consult with a qualified attorney to get specific advice based on your situation. The laws regarding inheritance and intestacy (when someone dies without a will) can vary significantly depending on your jurisdiction.
In many jurisdictions, when a person dies without a will (intestate), the distribution of their assets is governed by the laws of intestacy. Typically, this means that the deceased person's estate will be distributed among their closest living relatives, such as children, spouses, and parents, following a predetermined order.
If your sister is legally recognized as your father's child, she may have a legitimate claim to a share of the inheritance under intestacy laws. Her change of surname by deed poll doesn't necessarily negate her legal status as your father's child, especially if she was legally his child before the name change.
If you believe that your sister is not entitled to the inheritance or there are complexities in the case, you might need to consult a probate attorney. They can help you understand the specific laws in your jurisdiction, evaluate the situation, and advise you on the best course of action.
Keep in mind that inheritance laws and procedures can be complex, and family situations can be emotionally charged. It's crucial to approach such matters with the guidance of legal professionals who can provide you with accurate and personalized advice based on the specific circumstances.