I have a group of ex colleagues who had known each other for more than a decade. We were close back when we are young and unmarried. Always go outings and hang out. Only the past 2 years we have catch up like twice a year and we hang till over midnight. We are all married and most have kids now.

For me it’s okay. Especially if the bunch of friends is made before coupling or married. It’s their friends. And if you doubt them then I guess you choose the wrong partner.