I think it all depends. My sister met her wife when they were young and that SIL is one of my very best friends in the entire world. We’ve emailed or texted each other daily for probably the last 15–16yrs. But they had to get married in a rush because Mittens was like ‘no, I don’t LIKE gays getting married” so there was no real wedding beyond a court house ceremony.
I’m far less close to my brother’s wife. We get along and have a good time together but it’s not the same level of closeness. I don’t text her or email with her. And it’s not personal at all. I quite like her. She’s just not chatty like that and that’s okay. As long as she’s good to my brother and we have a fine time when we’re together, that’s a good level of relationship.