My girlfriend Jean, has 2 children from a previous marriage. Her and her ex-husband Matt had a rare mutual breakup, and were still cordial. He had to travel for work to South Carolina often, and was offered a position to move there. She couldn't move away due to having to care for her elderly parent. He actually lived fully in South Carolina for 2 years before they agreed to end their marriage. He eventually married another girl, Susan from down there.
She had split up with Matt more than 3 years prior to us getting together.
Matt's parents still lives in the area, so he would make trips up to visit the kids, and his parents about once a month or so, sometimes bringing Susan. Also, she and the kids would go down for a week vacation in the summer to visit.
At the beginning, I didn't want things to be awkward, so I would not be around when Matt was there to visit or she travelled down.
It wasn't until a few months that I found out, Matt (and sometimes Susan) would actually stay at Jean's house for the visits. I had assumed they stayed with Matt's parents or at a hotel. When I kinda asked about it, she explained that he had always stayed there since their break up. He sleeps in her son's room (when Susan comes) or on the couch. It's just how its always been.
I get that, and understand how it is just a common thing of convenience now for their situation. It was like that way before me.
As time progressed, I would come around and also stay the night some at her house during Matt's visits. Never was an awkward moment between us.