If your father was fit to make the will then it stands and you will have to hope that your stepmother does provide for you in her will. Your father has the choice to leave the house or at least his share of it to whoever he wanted unless the title deed provided for it to go to the survivor of them in which case the will is irrelevant. If there is no survivorship clause in the title deed and your father was not fit to make a will, and you would need medical evidence to prove that, then you could apply to the court for a reduction of the will in which case the estate would fall to intestacy and the rules of intestate succession would be applied. In other words the court can't rewrite the will to leave your father's share to you. It can only make the will invalid as if it had never been written. Happy to discuss. I hope that helps. Please leave a positive rating so that I am credited for my time.