I didn't realize how close my DH and MIL were until we married. At the time, my in-laws were stationed overseas, and DH did talk to his mom every day, but I didn't realize it, because they talked over the computer with instant messaging. If I had seen him, I would have just thought he was on his computer.
Once they moved back to the states, I realized that when my MIL is upset and needs comfort, she usually calls my BIL, but also often calls my DH. She rarely talks to my FIL. I think she might want to be strong for my FIL, like she always was during deployments orduring times they lived separately because of where he got stationed. She got breast cancer after she moved and my BIL was a pretty constant source of support for her, but she also leaned on DH. I don't actually think I minded it, until she started calling DH to comfort her for problems, issues, and worries she had about me.
I also didn't realize it, but everytime DH and I had problems, he told his mom we were going to break up or get a divorce. He now knows this is wrong. The psychiatrist we see for marriage counseling says this is a big step. At least he says he knows that. I don't believe it yet (that everytime he disagrees with me he won't run to his mom, and tell her we're getting a divorce which will bring out her mama bear instincts to protect him), but when you read conversations on your husband's account and see he's talking to his mom about how to get full custody with no visitation for you, then trust is a pretty uphill battle.
While we've been working on our marriage, our marriage counselor suggested we tell his parents that unless they agree to follow our boundaries, they cannot participate in our lives. They would not agree to this, so we cut them off. My husband cheats pretty often, but always insists he didn't mean to.
We tried to set one boundary before cutting them off. That was saying they couldn't call my husband up to talk about me. My MIL cried and refused and said she couldn't agree to that, because he wasn't somebody's husband-- he was her son. We said other words, she ended up yelling, so I ended the video chat and haven't spoken to them since the summer.
The holidays made DH want them in our lives again. I'm feeling inclined to agree as well, but I don't know how we should slowly go about it. I don't want to end up on the brink of a custody battle again.
EDIT: By "cheating" I meant we agreed to not talk or see his parents until they agreed to follow our boundaries. We came to this agreement in marriage counseling while under the direction of a psychiatrist. They were unable to follow the first boundary we gave them and MIL started screaming, so she never heard any others.
I say he "cheats" because our psychiatrist calls it cheating. Without discussing it with me, he is going against an agreement he made. If he wanted to have his parents back in his life, that's something we can discuss and then work to move forward with that action as a united front. Also, it is behavior he would not do in front of me, or else he would not feel the need to sneak. Every once in a while, I'll see him on the phone with an expression of guilt to his face, and he'll admit he's been talking to his parents. First he tried to say they only talked about finances, but I put my foot down and insisted we separate our finances. (DH makes over $100k a year, which is more than my FIL. Sometimes when they came to visit, they had to borrow gas money to get home. It's ridiculous that DH was taking money or help from them.) Then he said he had a question about what to do with his career and wanted to talk it over with his dad. Earlier last week, I asked if his parents knew about a very personal medical issue my mom had, because my MIL posted on my Mom's boyfriend's FB wall about it. (He accepted her friend request. My mom won't be friends with her online, after she accused me of being an abusive and neglectful mom and tried to get DH to file for sole custody.) My husband said he told them about my mom's private medical issues, but didn't know how it came up. He tried to sneak their Christmas presents into the house and told me they were from his grandparents, then changed his story and said it was from his brother. Then I saw the box they came in and caught him because it still had the return address on it. (My MIL told me keeping the kids away from her was unfair because of all the gifts they've given. I then talked it over with DH and we agreed his parents were no longer allowed to give us gifts until they understood that buying a gift is not the same as buying acess to people. We agreed to stop taking money from them, but he kept taking money from them for five months before it came out in our marriage counseling. Now, our finances are separate, though I suspect something is going on, because our bank had an issue with one of our charges and called my FIL, who called us to let us know about it. DH insists the bank would have no reason to do that, but I think if I finances were truly separate then that wouldn't have happened.
That's the kind of things I mean by cheating.