In Europe, the general rule was (with local differences, of course):
In the Middle Ages, girls could sometimes be married at the age of 12 or 13, boys at 14, or even earlier under certain circumstances. According to church law, betrothals were possible as early as 7 years of age. Especially from the nobility one knows historical examples of marriages or engagements of very young children for political purposes. However, such very early marriages were hardly the rule among the normal people.
Marriages were arranged by parents, relatives or the lord of the manor, and were therefore not based on the mutual affection of the bride and groom, but on dynastic, social or fiscal considerations. The average age at marriage rose steadily, and by 1500 was around 24 for men and between 16 and 21 for women. In marriages contracted for dynastic reasons, grotesque age differences occasionally occurred.
Generally people married among equals, people of the same class. Inferior wives, also called women "to the left hand", did not reach the status of the husband, were disadvantaged under inheritance law, their children remained in the lower status (they "followed the worse hand"; morganatic). According to court law, unfree women had to obtain the lord's consent to marry.