All minors, including newborn infants, must have their own passport. In addition to complying with the general requirements for applying for a passport, note the following additional requirements:

The minor must appear in person
In an effort to prevent international child abduction and improve the accurate identification of passport applicants, the Department of State requires the personal appearance of all minors applying for passports, even if the minor has previously been issued a passport.

Proof of Minor's Relationship to Parents/Guardians for a minor under the age of 16
If you  apply for a minor under the age of 16, you will need to submit one of the following documents as evidence of the minor's U.S. citizenship: a certified U.S. birth certificate (with parents' full names), a Consular Report of Birth Abroad, Form FS-240 (with parents' names), a Certification of Birth Abroad, Form DS-1350 (with parents' names), an Adoption Decree (with adopting parents' names), a certified copy of a Court Order Establishing Custody, or a certified copy of a Court Order Establishing Guardianship. Note that if the name of a parent or guardian is other than what appears on the document submitted to prove the parental relationship, evidence of a legal name change is required. Note further that a prior U.S. Passport is not considered sufficient proof of a minor's relationship to parents.

Parents must present Proof of Identity to establish relationship to minor under the age of 16
Each parent or guardian must submit one of the following: a U.S. Passport, a Naturalization Certificate, or a current, valid driver’s license, government identification card or military identification card. Note that a Social Security Card does not prove your identity. If you do not possess the identification listed, you will need to provide alternate proof of identity.

Proof of Consent of both parents
Both parents should appear together and sign the application of the minor under the age of 16. However, if only one parent appears and signs, that parent must submit the other parent's notarized Form DS-3053, Statement of Consent: Issuance of a Passport to a Minor Under Age 16 and provide a photocopy of the front and back of his or her ID. Alternatively, a parent who appears alone and signs must submit one of the following forms of primary evidence of sole authority to apply: Minor's certified U.S. or foreign birth certificate (with translation, if necessary) listing only applying parent; or Consular Report of Birth Abroad, Form FS-240 or Certification of Birth Abroad, Form DS-1350 listing only applying parent; or Court order granting sole custody to the applying parent (unless minor's travel is restricted by that order); or Adoption decree (if applying parent is sole adopting parent); or Court order specifically permitting applying parent's or guardian's travel with the minor; or Judicial declaration of incompetence of non-applying parent; or Death certificate of non-applying parent.

Signing the passport application
Applicants age 16 through 17 must sign their name on the application.  For applicants under age 16, a parent must sign for the minor by printing the minor's name on the signature line and signing the parent's name below the minor's name.  Do not sign the application in advance, as it must be signed in front of a passport agent.

Minors involved in custody disputes
Parents, legal guardians, legal representatives and courts can request that the Department of State Office of Children’s Issues register a minor's name in The Children’s Passport Issuance Alert Program. The form used is the DS-3077 Request for Entry Into Children's Issuance Alert Program. If a minor's name has been entered in this program, a passport will not be issued to such a minor without notification to the proper parties. For more information visit the Department of State's Children’s Passport Issuance Alert Program site.