Just for fun, it's worth pointing out that marriage itself is a human-created institution and not exactly "natural". But if we explore this rabbithole we then have to start asking what natural even means, and if man-made things are natural, and so on.
But it's an interesting point to include when thinking about such things, because it's a good reminder that most of these things are constructed and actually very context-sensitive (eg- arranged marriages were probably once more realistic in older configurations where family ties played a more important role in an individual's survival).
Family ties are still as important today as they were back then, which is why people ought to think more about their children and their mental health when they decide to part ways for their personal greed.
> Just for fun, it's worth pointing out that marriage itself is a human-created institution and not exactly "natural".
I would take it one step further and suggest that love itself is human-created.
I take "natural" to generally mean instinctual (raw emotional reaction), and as such any immediate (as opposed to a prolonged social feeling) reaction of sexual desire (lust) or pair-bonding instinct (nurture) can be categorized as "natural" - as opposed to socially sanctioned feeling-stories like love or institutions like marriage.