You need to be more clear about your circumstances. Normally a step-parent has no rights to a step-child, and no standing to bring an action for custody. Exceptions apply, particularly in California, but most states are pretty stingy with step-parent rights.

How is it that you have a custody case involving a step-child? (It sounds like what may have happened is that you tried to file one and the judge handling the guardianship said "no dice, you're a step-parent, but I'll consider giving you some visitation through the guardianship proceedings while we figure out what's going on.") Or are you saying "custody" when you mean "guardianship", with the goal of being made the child's guardian instead of the grandparents?

Where's the biological father, and what's his position on this?

I don't fault you for this, but you don't seem to understand what is going on in court, what your rights are, or the limits of what you can achieve. We don't even know what legal actions have been filed in court and, other than the guardianship, what actions remain pending. You need a lawyer. Check out these resources.