Contact the Vital Statistics office of the state where he is born, they can help you out.
The authorized birth certificate may refer to the Original birth certificate rather than the Copy of the Birth Certificate.
Why would you want to sign a birth certificate?
No. Birth and Adoption certificate are different
He should have a birth certificate that shows his parents names and one of those would be either your sister or brother depending on how he supposed to be your nephew. Also the birth certificate shows place of birth so if your sister/brother lived in that area at the time it increases the likelihood that it is the correct name. But if he does not want to deal with you, you can't force him to do so.
Yes
You haven't explained whose birth certificate. If it's her biological child then she must sign the birth certificate. The biological parents of the child sign the birth certificate.
A birth certificate is a legal document showing that a person's birth occurred and has been registered within the jurisdiction of the agency issuing the birth certificate.
Whose birth certificate?
Yes.
how much is an AZ birth certificate
under birth certificate form
You need a certified birth certificate, not a baptismal certificate. It is only important if you have no birth certificate and a letter from the state saying that there is no record after a detailed search of your birth certificate.