young tug, thank you. I didn't realize that consent was needed under 21. Have a number of entries where they only state full age or with consent of parents.
Consent was needed if you were 21 until about 1970 when the age was lowered to 18.
My husband and I both had to have parental consent in 1961.

Consent is needed, no matter what the age of either the bride or groom.

So where they are old enough to give their own consent to marrying, they show their consent by signing or otherwise making their mark.

So they need to be of full age, I.e. no longer of a minor age, to be old enough to give their own consent to marrying, BUT if not yet of full age, ie not yet having reached majority, then IF marrying, they need a responsible person to provide that consent to marry, on their behalf.
So if under age, they sign etc, and the officiating minister or civil official ought to also record the consenting detail.
JM