This is a very complex issue. So when is underage not underage?

There are at least 16 states in the USA where there is NO legal minimum age for marriage. A further 2 have a minimum age of 14 for marriage, and a further 5 have a minimum age of 15 for marraige. So, depending on what state you live in you can marry a minor. It was only in 1929 that the UK imposed a minimum age of 16 for marriage, prior to 1929 the bride/ groom had only to have reached the age of puberty.