This wouldn't work. Ex and I are divorced, I have physical custody of our child. However, ex still has to sign off on the passport application. I could see an ex refusing to sign off to ensure that the other parent doesn't leave the country with the child, or so that they can't "use child support money for an island vacation". There could be kids who just aren't able to get a passport issued. However, if they ran it like other your sports do and require a birth certificate to register. DS plays lacrosse. US Lacrosse requires a birth certificate for registration, his membership card includes his date of birth and which age level he plays. We have to show it at registration for all of his tournaments.