My brother and his ex-wife remained cordial and it was a good situation for their daughter. Friends is a relative term, I guess. They certainly didn't get along when they were married -- and they were married (and divorced) twice! To his ex-s credit, she remained in the same town and didn't remarry until their daughter was almost ready to graduate from high school -- didn't want to bring a step-father into the house.
"cordial" is NOT "friend" to me.....it means "tolerant"...LOL....which I agree is what is needed when children are involved....which is what I TRIED to be to my ex.