Rule 5.16.Designation of parties

Division 1. Family Rules · Chapter 2. Parties and Joinder of Parties · Article 1. Parties to Proceedings · Last amended 2026 · Last verified September 10, 2026

In one sentenceRule 5.16 fixes what the parties to a family law case are called and, case type by case type, who is allowed to be a party at all.

Full Text of Rule 5.16

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(a) Designation of parties

In cases filed under the Family Code, use the following designations for parties.

(1) Except as otherwise specified in this rule, the party starting the case is referred to as the “petitioner,” and the other party is the “respondent.”

(2) If the parties initiate the case by joint petition under Family Code sections 2330 and 2331 or section 2400:

(A) The first joint petitioner is referred to as “petitioner 1,” and the second joint petitioner is referred to as “petitioner 2.” For any Judicial Council forms that list the parties as “petitioner” and “respondent,” petitioner 1 should identify themselves as “petitioner” and petitioner 2 should identify themselves as “respondent.”

(B) If either party revokes the joint petition under Family Code section 2342.5(b), petitioner 1 will thereafter be referred to as the “petitioner” and petitioner 2 will thereafter be referred to as the “respondent.”

(3) In local child support agency actions, the local child support agency starts the case and is the petitioner or plaintiff in the case. The parent sued by the child support agency is the “respondent” or “defendant,” and the parent who is not the defendant is referred to as the “Other Parent.” Every other proceeding must be prosecuted and defended in the names of the real parties in interest.

(b) Parties to proceeding

(1) The only persons permitted to be parties to a proceeding for dissolution, legal separation, or nullity of marriage are the spouses, except as provided in (3), a third party who is joined in the case under rule 5.24, or a local child support agency that intervenes in the case.

(2) The only persons permitted to be parties to a proceeding for dissolution, legal separation, or nullity of domestic partnership are the domestic partners, except as provided in (3), a third party who is joined in the case under rule 5.24, or a local child support agency that intervenes in the case.

(3) In a nullity proceeding, the case can be started by the spouses or domestic partners. The case may also be started by a parent or guardian, conservator, or other person specified in Family Code section 2211. For this type of case, the person starting the case is a party and the caption on all papers must be appropriately changed to reflect that fact.

(4) The only persons permitted to be parties to a proceeding under the Domestic Violence Prevention Act are those identified in Family Code section 6211.

(5) The only persons or agencies permitted to be parties to a family law proceeding to determine parentage are the following:

(A) The presumed or putative parents of the child;

(B) The intended or natural parents of a child conceived through assisted reproduction as defined in Family Code section 7613 and sections 7690–7692;

(C) The gestational carrier, as named in a gestational carrier agreement, and the gestational carrier’s spouse or domestic partner;

(D) The child, as described in Family Code section 7635(a);

(E) A third party who is joined in the case under rule 5.24; or

(F) A local child support agency that intervenes in the case.

End

Plain-English Summary

The naming half is straightforward until the case is filed jointly. Ordinarily the party who starts the case is the petitioner and the other is the respondent. On a joint petition for dissolution or summary dissolution, they are petitioner 1 and petitioner 2 — and because Judicial Council forms are printed with “petitioner” and “respondent” boxes, the rule tells petitioner 1 to use the petitioner box and petitioner 2 the respondent box. If either revokes the joint petition, the labels harden into petitioner and respondent for good.

Government support cases have their own vocabulary. The local child support agency starts the case and is the petitioner or plaintiff; the parent it sues is the respondent or defendant; and the parent who is not the defendant is the Other Parent.

The second half is a closed list, and it is the part that decides motions. Only the spouses may be parties to a dissolution, legal separation, or nullity of marriage — with three exceptions: a nullity case started by a parent, guardian, conservator, or other person the Family Code allows; a third party joined under rule 5.24; and a local child support agency that intervenes. Domestic partnerships follow the same pattern. Domestic violence cases are limited to the people the Family Code identifies. Parentage cases list six categories, including the intended or natural parents of a child conceived through assisted reproduction, a gestational carrier and the carrier’s spouse or partner, and the child.

Frequently Asked Questions

Who is “petitioner 1” in a joint petition?

The first of the two joint petitioners. On Judicial Council forms that list “petitioner” and “respondent,” petitioner 1 identifies as petitioner and petitioner 2 identifies as respondent. If either party revokes the joint petition, petitioner 1 becomes the petitioner and petitioner 2 the respondent.

Can a new partner or a relative be a party to a divorce?

Not as of right. The only persons permitted to be parties to a dissolution, legal separation, or nullity are the spouses, a third party joined under rule 5.24, a local child support agency that intervenes, and — in a nullity case — the person the Family Code allows to start it.

What is the “Other Parent” in a child support agency case?

The parent who is not the defendant. The agency is the petitioner or plaintiff, the parent it sues is the respondent or defendant, and the remaining parent is designated the Other Parent.

Who can be a party to a parentage case?

The presumed or putative parents; the intended or natural parents of a child conceived through assisted reproduction; a gestational carrier named in a gestational carrier agreement, and that carrier’s spouse or domestic partner; the child; a third party joined under rule 5.24; and a local child support agency that intervenes.

Amendment History

Rule 5.16 amended effective July 1, 2026; adopted effective January 1, 2013; previously amended effective January 1, 2026.

(Subd (a) amended effective January 1, 2026.) (Subd (b) amended effective July 1, 2026; previously amended effective January 1, 2026.)

Source & verification. Rule text is reproduced verbatim from the Judicial Council of California. Adopted by the Judicial Council of California. Last verified September 10, 2026. · Official source

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