What does it change about their story at all?

We were all in multiple relationships, I dunno what to tell you. It is common in polyamory. Having kitchen table polyamory as we did isn't uncommon either, though not necessarily the norm as more formerly monogamous people try on a pair of polyamory pants for themselves. They often decide that they'd rather not know who their partner is dating. As for me and mine, we enjoy sharing space with our metamours. Seeing my partners being romantic with their other partners makes my heart feel super happy. And the people I date tend to feel the same way when seeing me happy with my other partners. 😊

That's the great thing about interacting with other people, you don't HAVE to understand it. It's THEIR story, and although you may not be able to personally relate to parts of it, that doesn't make it any better or worse than before.