Hardewicke's Act of 1753 was known to have many overly-strict requirements in it, causing many well-intentioned couples/families to fall foul of its constraints.
One famous protracted legal case in the 19thC involved the legitimacy of the 1795 marriage of the Earl of Belfast (from 1799, the 2nd Marquis of Donegall), George Augustus CHICHESTER (1769-1844).
Doubt was cast on its validity many years after the event, when a marriage of his eldest son in to the Shaftesbury family was being arranged in 1819.
GAC had married the (illegitimate, minor) daughter of the Sovereign of Belfast in some haste.
The full publication of Banns had been properly followed.
Unfortunately she had never had a formal guardian appointed.
Because of her "minor" status, a full conformance to the detailed letter of the Act required that the full formal permission of such a guardian had to be given.
[Her illegitimate status meant that the permission of her father was insufficient.]
After GAC pursued several personal legal law suits over many years, the issue was eventually only resolved by unusual amendments to the legislation being debated/approved through Parliament.
[It was unusual because its remit was made retrospective in time.]
This finally fully legitimised his 7 offspring, particularly the heir to his titles.
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Not surprised by those early limits on valid marriage ages.
Visited the Nelson museum in Norfolk last year, where it was stated that boys of 9 years old were meant to be self-sufficient - i.e. no longer a burden on their families.
Capt. Jock