Legal Question in Wills and Trusts in California

If title was in joint tenancy, then by operation of law the assets pass to your sister and a will would have no bearing. You may be able to file a petition that title was held that way as a matter if convenience if you have good facts to do so. You should speak with an attorney who handles probation litigation in the county where you father resided.

It may also be possible to sue your sister to throw out the deed - if your father was mentally incapacitated or was the victim of your sister's undue influence at the time he transferred the home into joint tenancy, then it could be thrown out. However, it's not an easy case unless you have good facts in your favor that would make it more likely a probate court judge would conclude that your father didn't understand what he was doing when he transferred the home into joint tenancy.

It is difficult to answer your question capably without seeing the deed and account title information. If the deed reflected Tenants in Common, there is a 50% interest stilll in your fathers name. If Joint Tenancy it transfers by right of survivorship, though this can be challenged. You need to get copies of the deed and other title information. You also need to determine what your sister intends to do. If she intends everything to go 50-50, this can be worked out. If she takes the position it is all hers, the title documents become essential. Either way, legal action is needed to clear title.