My estranged father died with property out of state. How do I get the deed if someone else illegally had him sign it over days before his death?

If you admit that you were "estranged" from your father, isn't it rational that your father would have wanted his uncle to get the property rather than you?  As long as he was competent and not under undue influence when he gave your great uncle the deed, he could do that.  Since this involves Texas property, you should post this question for a Texas lawyer to respond.