To further prove that the current idea of what marriage is wasn't always the case:
There's a lot more to be read here: Here's Why The Idea Of 'Traditional Marriage' Is Total Bullsh*t
Like most ancient governing bodies, Athens didn't legally define marriage for its citizens. Producing offspring was pretty much the only reason to get hitched -- as one man put it, "We keep hetaerae (courtesans) for pleasure, concubines for the daily care of our body, and wives for the bearing of legitimate children and to keep watch over our house" -- because the state did control movement of wealth through inheritance. It was so important to keep property within the family, Coontz writes, that a girl whose father died without leaving another male heir could be forced to marry her nearest male relative, even if she had to divorce her current husband.
Marriage wasn't even considered the most ideal union, at least according to the elite members of society. That honor went to -- drumroll, please -- homosexual partnerships, since married men and women weren't expected to provide emotional fulfillment for one another.
Confucian philosophers argued that the strongest family bonds existed between fathers and sons, or between brothers, Coontz writes. Marital bonds were a far second to familial ones, so much that a son could be beaten for siding with his wife (who was made to move in with her husband's family) and not his father.
One of the stranger marriage traditions to come out of any society is undoubtedly China's practice of "ghost marriages." To keep unmarried deceased relatives from being lonely in the afterlife, family members married them off -- to another without a pulse. The two were united in a graveside ritual, and the new in-laws kept in touch afterward. Despite being banned in China today, ghost marriages still happen.
For the rich, marriage was again a political arrangement between two families who wished to cement their ties and merge assets. Queens arranged marriages for siblings, relatives and ladies-in-waiting in order to create international support networks for themselves. In the 12th and 13th centuries, people believed that "love cannot exert its powers between two people who are married to each other," as the Countess of Champagne once wrote. Adulterous relationships, on the other hand, were the pinnacle of romance.
To the Catholic Church, marriage simply consisted of a man, a woman, mutual consent, consummation, and -- very important -- parental approval. Parents had so much control over marriage negotiations that in 1413, two Derbyshire fathers signed a contract in which the bride's name was left blank, because one father hadn't decided which daughter to marry off.
The plebs used marriage as a way of arranging plots of land, which were doled out in random strips. It was more ideal to have multiple strips next to each other, so you might hope your daughter could marry the neighbor's son. Traders and artisans in the same business often married each other to share supplies.
Young people rebelling against their stodgy Victorian-era elders did so by flaunting their youth and hotness, so in addition to marrying for love, ideal couples around the turn of the last century also had satisfying sex lives. By the end of the 1920s, Coontz writes, intimacy between two married people had become even more important than ties with parents. Meanwhile, critics penned newspaper columns titled, "Is Marriage Bankrupt?" and predicted that the increasing focus on sex would lead to the institution's demise in less than 50 years' time.
There's a lot more to be read here: Here's Why The Idea Of 'Traditional Marriage' Is Total Bullsh*t