Relationships, sexual or otherwise, are not subject to paperwork. The days of relationships, sex, or even reproduction being tied to marriage are long gone.
It’s stupid because the combination of singles mixers, tinder, and community events make it very easy to find a partner (keeping them is another story) but nobody wants to try. I’m of the opinion that porn has sapped their will to find women, even though it’s very possible to have a healthy relationship with porn and men have indeed had healthy relationships with porn throughout recorded history.
You can construct your family in a lot of different ways. Having a lot of friends, some very close friends, and zero lovers is a perfectly valid one.
At least, it was becoming such. Legally, there is more and more push back against structures other than one male and one female, who are each other's sole and perpetual means of support.