Is it weird that my (31M) ex girlfriend’s (29F) new girlfriend (29F) started hanging out in my friend group randomly?

After 7 years together, my ex and I broke up about 1.5 years ago. She started dating this other girl maybe like 9 months ago. And about 6 months ago that girl started hanging out in my friend group. And now she’s part of my core friend group and I see her a couple times a week. My never with her when she hangs out with us though

I’ve known this girl for probably 6 years. Never been close with her and never had the same friend group. Just seems random now she’s a part of my core friend group

Anyway we were all naked in a sauna together last week and she saw my penis. Just thought that was kinda odd