Considering the growing inequality between rich and poor, there’s evidence that the rich are more likely to marry and start families especially in the developed world. Consider this, if the rich can afford to get married then they can afford to arrange marriages. That’s been done for many centuries especially in Europe.
Whereas those of lower classes can get away with love marriages (marrying for love as called in the Indian subcontinent) but because they don’t have enough money. I remember these are also the classes most likely to cohabit for the same reason. Again we’re seeing a revival of sorts in the developed world for that reason.
As for the upper classes, there’s been a marked tendency to marry their children to aristocrats especially in Europe among merchant families. The Fuggers and Medicis were no strangers to this. These two also have strong desires to ennoble themselves, which eventually happened.
It’s going to get more common in the future whether if people want it or not, given what the rich can do with their money.