Legal Question in Wills and Trusts in California

Superior Court (Probate Division) of the county where he resided at the time of his death. You should consult an attorney.

Your objections would be filed in the Superior Court - Probate department of the County where your father was living at the time he died. You would file them in the same probate proceeding that I assume you sibling is opening. I agree with Michele that you should consult with an attorney. There are a number of somewhat complex issues that you will need to address to prove your case. You should also look for any assets that your father may have had in joint tenancy as that could control there disposition.

You can contest the will in probate court, and if other items were changed (like property deeds, life insurance policies, retirement plans, etc.) you can sue for the return of these to his estate in probate court as well.