Off my chest, am I overreacting?

Last night my husband and I were watching Instagram reels on his phone and he went to send me a video because we both laughed really hard at it and wanted to keep it, and that’s when I noticed there was a group message between some of his family and his ex and he was also added to the group. I immediately asked him what that was and he said he had no idea about it which I know to be true because all of the messages were unread. I told him that I’m not upset with him, he didn’t know and didn’t create it. However, I am so hurt with his family and feel like I need to create boundaries for my own peace of mind. I am highly uncomfortable and weirded out with this, they can all maintain their friendship with her but they should not involve us with it. I understand his ex is his sister’s best friend, I don’t ask or expect her to stop being friends with her but why add him to this group? They also have never done something like this with me involved. We’ve been together for 3 years, are married and had our first baby 16 days ago. I’m just really hurt and needed to vent and see if I’m overreacting about this.