Do my boyfriend and I have to be married to adopt a child?

My boyfriend and I have been together 8 years and want to adopt. I can’t have kids of my own and I’ve been married once before and it ended in an ugly divorce. I don’t want to get married again, and my boyfriend is fine with that, but we do want to raise children together. I have started researching adoption options but it appears that we might need to be married before the California Department of Social Services will let us adopt. Someone mentioned to me that it might be possible to adopt if my boyfriend and I are registered domestic partners. If we live in the Sacramento area, is it true we have to be married? If so, will a domestic partnership allow us to adopt and how do we go about registering as domestic partners?