Yes they can,
Because when my aunt got married, her marriage papers had to be signed my the best man and maid of honour, which was my other aunt and her sister
No, children under 18 cannot sign as a witness on a marriage certificate.
A member of the same family by birth, marriage, or adoption.
You sign your own marriage certificate. In order to do that you have to obtain a marriage license. The license requires you to be 18 in the US and a vast majority of the rest of the world.
No, not legal.
A marriage witness can be anyone who is present at the ceremony and is willing to sign the marriage certificate. Their responsibility is to witness the couple exchanging vows and signing the marriage certificate to validate the marriage legally.
Only a guardian or parent can do this.
No, the marriage has to be formalized by a member of the clergy or a court official. They sign the license and it is filed with the clerk.
no
guardianship over to a particular family member
To endorse a check to a family member, you need to sign the back of the check and write "Pay to the order of family member's name" followed by your signature. This allows your family member to deposit or cash the check.
Executor fees are set by law. The family does not have to sign off on them.
It must be signed by ordained, and returned to the court for registration.