If you, like me, are a fan of Elon Musk's advice to make more babies, then you'll need a bride (or a man if you're the bride). But like any relationship, it has to come from two sides. If any of the partners does not want the relationship, the other should accept that decision, and not try to force it like Biff in Back to the Future tried to get Marty's Mum to be his wife. Stalkers are in the same category as bullies, exerting undue influence in others' lives against their will.
But a relationship should be like both parties want it. Some may want legal marriage or even religious marriage, but if a couple is completely comfortable to live their lives without such restrictive rules, they still have the free will to do so. And by now we have mostly reached a culture where children born from such a relationship have all legal rights to exist!