I dont really have a lived experience to go by in this. I dont have an ex spouse/partner, because the only person I was involved in a romantic relationship with, I remain involved with him, and even though things have changed over the years, they have also remained the same.
I guess no other relationship really has the concept of an ex, particularly a familial one. You can hate your parents, siblings, drift apart from them, but they remain whatever they are. The role does not go away. A husband may cease to be a husband and become a friend, but a mother becomes a friend in addition to being a mother.
So this romantic/marital relationship is the only one which offers an exit option for you. In other relationships, the thought of the exit option itself is repugnant. I remember feeling very angry, when before we adopted our child, the agency kept asking us if we were sure we wanted to adopt this child. I wanted to ask them on what basis does one reject a child. But they also told me that sometimes, adoptive parents had returned children to them, saying they were not suitable.
Yes, even the thought feels weird right. But at the same time, the thought of a giving up on a marriage or a relationship we have been a part of for quite some time is not so weird. I am not condemning the idea of divorce or separation, just wondering about how the availability of the exit option influences the course of the relationship, for better and for worse.