The ages were 12 for a girl and 14 for a boy, but infact boys at 14 usually would be indentured or apprenticed and were not allowed to marry, not until they had finished their seven year apprenticeship, that is at 21. Girls were often also indentured or apprenticed, and the same applied, there were extremely strict laes that were instigated if the appretice broke the terms of their indenture, and anyone breaking laws laid down by the Ecclesiastical court were dealt with harshly, and that included falling pregnant out of wedlock and producing a ******* child, especially if that child was a burden on the Parish because there was a drain on the poor relief, a child obtained a right of settlement in their parish of birth, and any unmarried pregnant woman would be examined before the local JP to establish her Parish of Settlement and she would be escorted out of the Parish before she gave birth. Sorry, rambling into one of my lectures now, but anyway, the marriage of young adults under the age of 16 was primarily found in the gentry classes, who would secure land and inheritance through joining families .
In 1837, when civil registration took the responsibility of legal marriage from the Anglican Church, mariages had to be between people of 16 or over and under 21 they had to have parental consent, however, if you find the entry 'of full age' on a marriage certificate, this should mean 21 years or over, but invariably it means they were infact under 21, the consent of the parent or guardian prior to 1837 was given through a marriage Bond which is an excellent source for ascertaining the identities of people with similar names in an area.
Sorry, I could write for hours on this but I won;t.