With parental consent a 12 year old can marry another 12 year old in any other states other than Delaware and New Jersey.
New Jersey and Delaware do not allow underage marriage in any exceptional circumstances even with parental consent.
But if you're in any other states other than New Jersey and Delaware then you can get married at 12 or above with parental consent.
The country that has the lowest marriage is Estonia.
Estonia is the country that has the lowest marriage age in Europe with teenagers able to get hitched at 15 with parental approval.
However with parents consent even those 16 and up can get married in most of the USA.
However both the bride and grooms parents must consent to the marriage and not just one set of parents.
If both parents of the bride and groom do not consent to the marriage then they cannot get married until they turn age 18 or get emancipated.
You can get emancipated from your parents which makes you legally responsible for anything you do and then you don't need your parents consent.
But if not you need to wait until age 18 to get married without parents consent.