Ms. Paddock,
Are you certain that the trust is irrevocable. That would mean, generally speaking, the trust you are referring to was not created by your father.
If in fact this is a revocable trust which is a common estate planning tool, he can change it anytime he wants to and he can disinherit you if he wants to and it is not related to your sister’s death.
If the trust is truly irrevocable, he would be able to change the terms of the trust if he had been given a special or limited power of appointment to change the terms of the trust usually to take effect after he dies.
Good luck.
Answered on Sep 22nd, 2019 at 5:33 PM