In California and elsewhere, a divorce decree doesn't terminate parental rights. It only establishes terms for those rights when parents are no longer married and living together. A parent can have minimal, supervised or no visitation at all with their children yet still have parental rights, unless and until a court order legally severs the parent-child relationship. The custody terms of a decree only dictate when and how a parent spends time with his child.
In California, the custody terms of a decree dictate which parent a child lives with, if the child doesn't divide his time equally between his parents' homes. The decree establishes visitation and parenting time for the parent with whom the child doesn’t live most of the time. It also spells out which parent makes fundamental decisions regarding their child, or may establish that both will do so. Typically, there are only two parties to a divorce decree: the parents. Therefore, when one parent dies, the decree's custody terms no longer have anything to govern. Legal and physical custody both automatically revert to the living parent.
Certain circumstances can interfere with custody automatically transferring to a surviving parent. If a court has terminated a parent's rights, he's no longer legally the child's parent; therefore, custody would not revert to him if the child's custodial parent died. California typically only terminates a parent's rights due to factors of abuse, neglect or endangerment. A parent can't voluntarily waive his rights, unless it is to allow someone else to adopt his child. Additionally, if the terms of a custody decree are modified post-divorce to give sole legal and physical custody to one parent, the other parent does not automatically receive custody if the custodial parent dies. Such a post-decree modification would typically require that something occurred in the parent-child relationship after the divorce to make such a change necessary.
In the event the court has terminated a surviving parent's rights, or changed the terms of the decree post-divorce to award full custody to the deceased parent, California law allows third parties – such as grandparents or other relatives – to intervene. They can also intervene if they believe the other surviving parent is unfit for some reason, even if he's not statutorily barred from automatically receiving custody. California courts base such custody decisions on the best interests of the child. The family member asking for custody would have the burden of proof to establish that placing the child with the surviving parent would cause him harm. The third party would have to file a custody proceeding with the court separate and apart from the divorce decree.
Establishing for the court that a child would not be better off with his surviving biological parent can be a difficult undertaking. The custodial parent can make it easier for other relatives to step in through a few estate-planning measures, such as naming another guardian for her children in her will. She can also include her written reasons, either separately or as part of her will, for the nomination of the guardian. She can explain why she believes her child's other biological parent is not fit to raise him. Such efforts wouldn't control the court's decision, but they could be a factor in a judge's determination. If the court approves the custodial parent's nomination of a guardian, it wouldn't sever the parental rights of the surviving parent. However, the child would live with the nominated guardian.