In the event of a serious accident or when medical negligence results in a death, California law defines who is allowed to be a party in a lawsuit for damages. Only the persons specifically indicated in California Code of Civil Procedure § 377.60 have the right to maintain a wrongful death action. Those rules allow for a surviving spouse or registered domestic partner and children to maintain an action for the death of a husband, wife, father or mother. But in some cases, those rules can also include the children of deceased children [grandchildren], minors who were dependent on the victim and possible step children. Parents can bring an action in specific circumstances and others who may have been dependent on the victim for one-half or more of their support in the 180 days before the death.
As you can see, the rules of who can sue for a death are determined by the laws of the state of California. They can be complicated and it is wise to consult with an attorney to determine, in any given case, who has standing to sue and who does not.