As directed by Public Law 106-113 and 22 CFR 51.28, to submit an application for a new passport or to renew the passport of a child under the age of 16, BOTH PARENTS or the child's legal guardian(s) must appear at the passport office (or post office) and present the required documentation. After a divorce, even with parents who were ordered to share Legal Custody, one parent may not be inclined to help out the other parent when he or she is making plans to vacation with the children. So what do you do?
1) Have your custody orders modified to take legal custody away from the uncooperative parent, or have the order modified to include ramifications if a parent unreasonably withholds his/her consent. If you are currently going through a divorce or parentage action, keep this in mind. Make sure your judgment specifies the parameters of Legal Custody, if it's going to be shared, and make sure your judgment has penalties for unreasonable failures to cooperate when both parents are required to consent to a minor's activity or travel plans. OR
2) Have the parent provide a notarized written statement or DS-3053 [http://www.uspassporthelpguide.com/wp-content/uploads/2013/06/ds-3053.pdf] consenting to the passport issuance for the child. Note that if there is more than one child, you need a separate statement or DS-3053 for each child. The notarized statement or DS-3053 cannot be more than 3 months old and must be signed and notarized on the same day, and must come with a photocopy of the front and back side of the signing parent's government-issued photo ID. OR
3) present "primary evidence of sole authority to apply". If you have sole legal custody, you do not need the other parent's consent to apply for or renew a passport for a child under the age of 16. The passport office or post office will want proof. Bring your divorce judgment or parentage judgment with you that shows you were awarded 100% legal custody. Again, if applying for more than one minor's passport, make a copy of the judgment for each application. OR
4) A written statement or DS-5525 (made under penalty of perjury) explaining in detail the second parent's unavailability. [http://www.state.gov/documents/organization/217450.pdf]
Here are a couple tips for being fully prepared to renew or apply for minor's passports: The children for whom you are applying must come with you to the passport office (or post office, if applicable). Bring their original birth certificates, proof of U.S. citizenship, proof of identity (plus a photocopy of the ID), recent color photograph that meets passport requirements [FedEx Office can help you with that], and your check book. Yes, you can pay with credit or debit card, but there's an additional fee for that.
Safe travels ...