Being friends with your ex's is a huge red flag.

Personally, I don't think so. I'm cool with a few of my exes because we didn't hate each other or hurt each other, just better off as friends. My ex-husband/son's father and I get along fine for our son.

To me it shows maturity. It's when people complain about their exes that it becomes a red flag for me.

People that make enemies out of old lovers scare me.