I'm no expert either, but underage marriages don't count anywhere, although they're permitted in some bits of some religions n/inc Islam.
@frazzledasarock oh I see re the bride gift. I'd like books too. Thing is, the history of marriage payment in the UK is a long and dishonourable one, and that's why specific payments about the bride are illegal, as they are in Islam.
You start off with selling the bride, which no one has ever approved of but went on like anything. Slavery, simple.
Then you move onto marriages made for land and property consolidation which lasted for centuries until the UK got primogeniture ie all the females were stripped of their property expectations because the oldest son got the lot (also to maintain military power and county wealth).
Then you get to the stage where the male child gets the land and the girl gets the money. People had specific sums settled on them when they 'came out' ie debuted in society.
Jane Austen's Emma had £20k, famously. Not so famously, Austen herself had £0.00 as her father gave the lot to his DS and DIL, and Austen couldn't marry as she had no dowry. Women really did get stuck if they had no dowry.
Both sexes put up with this for a long time - men were told who to marry too.
In the 19th cent. thanks to the industrial revolution, land stopped making so much money, and British girls were kiboshed. That's why our aristocracy married American heiresses - they had buckets of cash from railroads and factories, whereas the wilting English roses had a couple of ornaments and barely enough to pay the scullery maid.
Not until 1857 (or thereabouts) was the Married Woman's Property Act made legal, where wives could own their own property, children and cash. Until then, you were at the mercy of your husband - you paid a lot on marriage that was supposed to be given back when he died/you left but no one ever saw their settlement again.
Nowadays all estates are businesses and in trust so it doesn't make much odds who you marry - nothing can be lost via divorce. .