So here's one for ya...DH contacted his ex and asked to compare insurance plans since it's open enrollment and we're wanting to move the kids over to my employer's plan.  He knows nothing about the plan his kids currently has, even after repeated requests for the info.  She went nuts.  Refuses to send info, lied about open enrollment being over already and hung up on him 3 times.  He is still only paying CS for his youngest, but voluntarily pays $$ every month to cover his 2 over-18 year old kids as well under her new husband's plan.  Again, he knows nothing about coverage, co-pays, deductibles, etc, but she will every once in a while tell him he owes $xx for this or that for his daugher, which he pays.  We even asked one of the older kids what insurance they have - he didn't even have his insurance card on him, telling us "oh mom has all that stuff", and he never goes to the doctor.  Their divorce agreement says that DH will carry insurance if he is able to at a reasonable cost, and says nothing about covering the kids past 18 - he does it because it's the right thing to do and he's able to.  The plan I have is excellent, and she has said in the past they have "crappy" insurance.

I told him we can go ahead and enroll the 3 kids and he stops paying her the extra $$ for insurance in January, and stick to the CS ordered in their settlement.

The rub is that he's concerned she'll take him to court to increase CS on the youngest, 15.  The amount that he's paying is less that the court would probably order, and more than what he's giving her now that includes the kids' insurance.  She typically is just a screaming bully until  she gets her way, and rarely follows through on any threats.  She hasn't tried to get an increase since they divorced over 5 years ago.  This is pretty much the last area of control she has over him, so it may push her over the edge.