Good morning from Texas! My family set-up is: my father, my mother (his wife), his “main” girlfriend and 2 “secondary” girlfriends which get changed usually every 2-3 years. Yes, we all live together in the same house - though it’s a big house - so it doesn’t feel crowded. It’s not a religious thing at all, we’re atheists.
That’s fair enough, don’t worry about it.
The reason I ask though, is that there is a difference, and I do think it’s something that you’d benefit from exploring critically, not with a bunch of strangers online, but with yourself in your own time as you grow older and start forming your own relationships (I saw you mention that you’re monogamous yourself, that’s cool, this is less about that though and more about recognising potential imbalances in relationships in general, and the issues those can cause).
And just to be clear - I’m not assuming there is anything wrong or unhealthy or anything like that about your family, non-nuclear/“traditional” families are perfectly valid, and I essentially know nothing about you and your lives. But I do know that we live in a society where men and women aren’t treated or socialised equally, and that recognising this and how it impacts on our lives is both important and beneficial, even if slightly uncomfortable at times. E: and to be even more clear, this is an examination we all can benefit from doing, since all our relationships are impacted.