If your father desires to change his Will to make his caretaker (a presumed non-relative) the heir to his entire estate the beneficiary, you need to be concerned about your father's mental state and perhaps undue influence by the caretaker to get his estate after his passing.You should immediately consult with an attorney concerning elder care issues and estate planning about your father and undue influence issues.His treating physician should be consulted about his mental state and ability to to fully understand the effect of changing his Will where the caretaker would be a the sole beneficiary. Potentially, you might have to file a petition for a custody over your father's assets and person if he cannot take care of himself.Terminating the caretaker's position is an option as well if you can do so.