Codependency Support Group
Codependency is defined as someone who exhibits too much, and often inappropriate, caring for another person's struggles. A codependent person may try to change, or feel shame about their most private thoughts and feelings if they conflict with the other person's struggles. If you are on a journey towards self-love, this support group is for you. Join us and find others...

What I see is that you are confusing the concept of "boundaries" as many people get them confused.
A healthy boundary means a boundary on our self and ONLY on our self.
Putting a so-called boundary on other people is what we call you being controlling.
Your ex-husband wants to join that group then that is NOT for you to control.
For you to control as your own boundary is that you accept the new dynamic and you interact as a mature adult with your ex and with the Admin and with everyone else.
Just control your self is the healthy boundary - not control the group or the members or control the ex.
When you become the dictator then you become the abuser.
You can not speak with your ex on the same FB group means that his presence alone controls you and controls your reactions.
HERE is a link about boundaries that I recommend = https://independentfew.wordpress.com/2015/02/03/boundaries-walls-and-denial/
And I do see such things as a "sign" as in it is sign that now is the time for you to leave that group, because you have obviously invested far too much into that group when you can not handle your ex to join, and many people have their ex living close by and dating one of our ex friends too, but you are knocked over just by your ex joining a FB group. For you to leave that group as your ex joins that group would be a much more healthy boundary on your self instead of trying to control the group and controlling your ex.
Control issues are a far bigger problem for everyone than are uncomfortable feelings.
And more as a sign for you to move on and away from that group is that I like to see those kind of signs as coming from God telling us that it is time to move on.
What you are doing is fighting against life-events as if your fighting can control the dynamics, and yes you can but it will hurt your self far more than anyone else.
That administrator of that FB group is being an enabler for living wrong, and we all have to step aside from the enablers in our own lives if we want to do the recovery right.
Just sharing my opinion here - and nothing personal.
It did seem like trying to control the situation a bit which is why I posted, but I'm not sad that I set the boundary. I am not at a place in my detachment from him where I can peaceably get along with him.
In the past I gave up friends, education, jobs, opinions, desires, you name it, anything and everything, just to make him happy and it caused my detriment. In this case,allowing him to join the group would actually be backsliding to my old codependent ways.
I need support in my life and shouldn't have to give it up just for him.
When codependency is not treated correctly then they turn into the same kind of abuser that abused them.
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Starfish ~ I like your comment except this one line:
" ... he would first consult with you and get permission to become a part of the group. "
Some man would ask his ex-wife if he can join a public group on Facebook.
That is not realistic.
But setting the boundary ultimately be doing what’s in your best interest , that may be to leave the group if your request is not answered the way you like and you don’t wish to have that sort of interaction with him , you can’t control the outcome of that .
Anger can be used as a defence mechanism if we don’t take any action .
I hear you and do agree with you, but I also recognize that I'm not able to function above the level where I'm at now. I can only do what I can do a little bit at a time. If I tried to force myself to do more then I know I am capable of then I think that I will set myself up for failure.
You are still avoiding the fact that you could put a healthy boundary onto your self instead of controlling the external events and keeping your ex out of a support group.
The thing is that you do what is "good" for you and "not good" for the other person(s) and so you are acting as the dictator and you are becoming the abuser.
Other people did such things to you, and surely your ex did such things to you, and now you have the power to do it to him as you see he deserves it and thereby you are being abusive.
People who were abused will become abusers.
Healthy boundaries mean just that they are healthy and productive and never hurt or hinder any other person.
Surely it feels great to have that control over your ex, but that control makes you into the villain and he is now your victim.
Abusers always feel "good" about what they do, and it is a sickness.
Do not do unto others what you would not want done unto your self.
Peace.
Why my ex would go to great lengths to make sure that the rest of the world loved him, he used me as his punching bag (figuratively). He treated the rest of the world like royalty and saved up all his anger, garbage, and hate, and dumped it on me. I took care of 98% of his physical needs and he treated me like dirt in return. I took 16 years of that before I decided to leave. When I did leave, at one point I thought I might not make it financially. I became suicidal at the thought that I might have to go back to him in order to survive.
When we divorced he married one of my close friends 7 months later. They were actually dating while my divorce wrapped up and didn't tell me. She was still pretending to be my friend and advised me in financial matters concerning my divorce which would benefit the both of them afterward, all the while secretly dating my soon to be ex-husband. Then after they married they spent several years telling my disabled children disgusting things about me, stirring my children up just before they came over to my place to visit causing chaos every time. One time exasperated while standing outside the courtroom I asked him, "Why are you doing this to me?" He yelled at me, "Because you deserve it!".
There is a reason why I had to go no contact from him in any form aside from emails. I had to block his wife and send her a cease and desist letter because she wouldn't stop trying to text me and message me hateful things plus threatened to come over to my house to "set me straight."
I realized just recently that even though I have been separated from him for 9 years, I still beat myself up daily for not leaving earlier. He doesn't have to abuse me any more. I'm continuing the abuse myself.
It's only been in the past two years that I have been able to interact with him at public events and have short, civil conversations without feeling angry every time.
While it's very easy to be on the outside and view the situation without emotions, making judgements, I'm not at the place in my recovery that you are arguing I should be. This is a step process and I still have a lot of emotions to get through and resolve before I stop trying to control my surroundings in order to have peace each day.
It may sound like I am making excuses, but I know what I can handle and what I can't. I have a good understanding of the progress I have made and how far I need to go. I am taking it one day at a time.
You can not handle doing what is right to do, but you can handle taking another shot at your ex husband as you can handle that just fine.
This is just another example of why that group is not healthy for you and that you need to leave that group.
That group is not enabling you to better your self but instead it is enabling you to keep doing wrong.
That "friend" who is the administrator who asked you to decide about your ex joining that group is an unhealthy enabler no matter how great of a "friend" they might appear to be.
Link = https://psychcentral.com/blog/what-is-the-difference-between-supporting-and-enabling/
You have your own opinion. I have heard it. I have stated what I can and cannot do at this time.
I have heard your point of view, understand it, and agree, but that doesn't mean I can suddenly propel myself several steps forward to do something that I am not prepared to do simply because you keep restating. You have decided that I am an abuser and that is now the only way you will see me. So there is no further discussion after that point.
If you wish to debate this further you should start another thread and invite others to discuss it with you.
My recovery did not really start until I was 40 years old and I was and still am irritated that my first 40 years were lost, and I say the years were taken away from me, so if I want to catch up or make up for lost time or if I want to get stuff done before I die then I have a severe urgent hurry to work on myself and for me to get my stuff done ASAP.
The very notion that I can wait until tomorrow or maybe next year is a condition which I can not accept.
I have loved ones / family members who wait and wait expecting life to fix itself and that is the biggest mistake that I can imagine.