So you have a problem with your inheritance, what are you going to do about it? That’s a tricky question because every case is a little (or a lot) different. Mainly it depends on the type of estate planning device you need to overturn, challenge, or validate.
For example, if you are dealing with a Trust, then you need to file a Trust action. If you want to contest a Trust or a Trust amendment, then you need to file a petition under Probate Code section 17200 seeking a determination of the Trust tems. That petition is filed in probate court, and it must include your legal basis for challenging the Trust or Trust amendment (i.e., lack of capacity, undue influence, or fraud).
If you are dealing with a Will or a Will amendment (called a codicil), then you have to file a Petition for Probate and a Will contest objection. Sometimes you have to file both a Trust action to overturn a wrongly created Trust, and then file a Will contest because there is a pour-over Will that gives everything back to the wrongly created Trust (it is a vicious circle, or catch 22).
If you are dealing with a joint tenancy asset that is wrongly going to just one surviving joint tenant, then you may have to file a Petition for Probate to open the estate and then a Probate Code section 850 petition to transfer the assets from joint tenancy to the estate for distribution under the decedent’s Will.
In addition to all these different ways to proceed, there could also be a claim for Financial lder Abuse under the Welfare and Institutions Code to add to the mix. An elder abuse action is technically a civil claim that can be brought in probate along with your Trust contest allegations.
The bottom line: if you have problems with your inheritance you have to map out (1) what you are attacking, and (2) how you are going to attack it. Once you know in what direction to head, then you can get to work to fight for, or protect, your inheritance.