Cameran has it right with Thomas and Kathryn being the "hot mess express".
I remember watching their "relationship" unfold and wondering what in the heck Thomas was getting himself into with her. He seemed so needy and like he was not seeing the forest through the trees to have some fairy tale romance and future with her. The relationship all happened way too quickly and neither of them really knew the other one before they jumped into their domestic nightmare. They both have buyer's remorse but there are two kids attached so they have to both man up and be adults about the situation. It's something I think Thomas can do. I really do. As gross as he is and as misogynistic as he is, deep down, he wanted those babies and would work with Kathryn if she were at all mature. But she is a 20 something hot head who seems hell bent on seeing slights and digs at every turn. She could gain perspective if she got herself off this show, into rehab and away from people who don't have her best interest at heart.
On other note, Kathryn constantly acts like she knows Thomas better than anyone else in the world. That she "gets" him in a way that no one else does. They only dated for a few short months and haven't really spent quality time together since. She's creating a narrative to fit her twisted mind and it seems like the cast buys it. She also acts as if having kids exalts her to a position where her actions are above reproach and her motives are all pure. Having kids means you squeezed a baby out, it doesn't qualify you for anything else. Her actions and inability to see any fault on her part in any of her interactions and her complete self absorption will make her a horrible parent. Those nannies are earning their keep!
Thomas is truly gross, but he's in his 50s, served in statewide elected office, is from a named political family, runs a successful commercial real estate company and is an adult. He gets a pass from the cast because he owns his truly horrible stuff and they forgive him when he comes hat in hand and apologizes. And I am going to guess that each cast member has way more positive interactions than negative. I doubt that's true with Kathryn, except for maybe Craig and Shep.