Legal Question in Wills and Trusts in California

Do you have a copy of the trust document? The trust document will control who receives from the estate.

You mention that your cousin is the Sole Beneficiary. Is she listed as the only person to receive from the trust? If that is the case, you probably have no grounds to challenge the trust.

Children do not have a right to inherit from their parents. Omitted heirs are children born after the will (or Trust) was prepared and spouses who married after the date of the will. Was your father a beneficiary in prior versions of their estate plan? Could the omission have been a mistake caused by some cognitive issues? Perhaps, but not likely and unfortunately very difficult to prevail because as noted above, your father had no legal right to inherit.

The issue is the circumstances surrounding the creation of the trust. How old were your grandparents? Did they suffer from dementia or Alzheimer's? Did your cousin who inherits everything pick the lawyer, drive them to the appointment and sit in on the meeting? What kind of relationship did you have with your grandparents? There are many factors that impact on whether or not you may have a good case.

What's supposed to happen is that the trustee should give you a notice under Probate Code section 16061.7 as you are one of the persons who would inherit from your grandparents if they didn't have an estate plan. This notice triggers a 120 day countdown on your right to file a court petition challenging the validity of the trust. Keep this in mind, because if you wait too long, then you can't do anything even if there's a case.