Legal Question in Family Law in California

Its not that simple. No its not needed to do it. As it can be done without his agreement. I'll explain...

Although you're the parent you still need him to either sign the petition or you will have to proceed without his agreement. If you proceed without his agreement he could be contesting it. If it is contested the change has to be shown to be in the best interests of the child. Generally removing a father's last name may be considered detrimental to the father-son relationship, which as you indicated is already seriously lacking. A lot depends on whether he contests it.

If he never signs the petition, does not contest it, and your attorney complied with the family code and uniform parentage act, then the court will change the kids last name (but not from the birth certificate, it is hyphenated).

I agree with the above with one important and sometimes expensive addition. If he doesn't join with you in signing the name change petition (consider hiring an attorney) then the following applies. He must be properly served with the Name Change pleadings, i.e. If the other parent lives in California, you must have someone serve him or her in person. If the other parent lives outside California, you can serve him or her by certified mail, return receipt requested. But, remember, you can NOT mail the papers yourself. If you can't find the other parent, then you will need to do a "due dilligence" search. It is usually cheapest in the long run to pay someone for this. You should get the proof of service to the court at least a week before the hearing.