Did you know that Grandparents have rights to visitation with their grandchildren in California?
If you can prove you have an emotional bond with your grandchild, and if you have the approval of only one of the child's parents, you can ask the court for a specific weekly or daily visitation schedule with your grandson or granddaughter if the court finds it is in the best interest of the child. Many grandparents raise their grandchildren for years, only to have them taken away by a parent who merely regards them as convenient day care providers. You can even be Joined to a Divorce or Parentage action as a party, so that if one parent is on drugs, and the other in the military you can keep a child safe until your soldier returns. However, if competent parents are still together and oppose your request for visitation it is presumed not to be in the child's best interest. Then you might ask for Guardianship, which has a higher burden of proof, and requires a showing of unfit parenting.
There are many more details, as you can read for yourself in Family Code 3103
, if you click on the link.