I know, sigh.
But 12/13 years... I just had a 10/13 year anniversary with my Spouse (10 married, 13 together) and this type of story of yours is exactly what I wonder about: will i wake up one day and find out my partner is not the person I thought they were?
I have quite a few friends who are going through this. People who have been together for YEARS, suddenly their partner becomes this stranger in their life. It can be anything from finding out they never liked your cooking or your favorite sexual position but only went along with it to please you, to full-blown domestic violence involving restraining orders and child-custody battles... But It makes me look at my two partners and go, "Are you next?" (we don't have kids but it doesn't have to be about kids - I have cats and it's always in the back of my mind that Spouse will get tired of the mess and the allergies and move out because of the cats... at least their other partner has dogs and Spouse is also allergic to dogs, so it isn't like they can just run to their other partner to escape, LOL). I wonder if my fabulous spouse is going to turn into some kind of monster and beat the shit out of me for no reason... This CAN happen, it DOES happen, and if it can happen to other people, it can happen to me.
That's why I write these things on this thread. It has mostly to do with me and not so much to do with the OP's relationship. But getting answers as to what the underlying causes are gives me some hope that maybe maybe my relationship WON'T end that way.