Understanding it does require getting out of the pre-designed mental box designed by monogamy.
But-as an example. I have two men, we all live together. I have one child biologically from each (and one of my own from previously). We're raising all of them together (and have been for over 10 years).
ALL finances are in one shared account and we have paperwork designating all property to the three of us equally....
So yes, they are both my primaries.