I have two significant others, I am very close to the family of one, they invite me over all the time and treat me really well, I feel very welcomed. We don't always have similar personalities or values, but we get along well.
My other partner's family lives in Texas, and except for her mom, they don't know she's dating anyone, much less that she's queer and in a polyamorous relationship... I don't think we'd get along amazingly, we have very little in common, but I bet I could have a friendly, civil time with them as long as they didn't know I was dating their daughter.