Gaslighting ex and child

[movetoistanbul]

My ex husband (left him for cheating with a prostitute, a woman he picked up from a restaurant for anal and then exchanging love poems with a 19 year old - also his family was abusive physically and one brother sexually). Now thank god we are divorced. But he's too busy to split the assets but that's another story. I was on antidepressants for 5 years of the 10 year marriage and the remaining five years I was either pregnant or breastfeeding.
While I earned, he earned more and was successful in his career, which made him think that he deserved my undying love and commitment and forgiveness.
Sex was mediocre at best.
So all in all a fantastic catch!
Today as I had the kids for Christmas messaged to say that he was thinking of getting married. I told him that it's not for me to know but for the kids to know. He then went on to message the very anxious ten year old that he's thinking of getting married. The kid then come to me, asking 101 questions and increasingly got agitated. My family member that I am visiting and who is a social worker working with kids was there too and answering questions and trying to reassure my daughter that everything will be fine. It ruined our night. I kept a normal face and answered questions patiently and calmly, I gave example of my own step mum and how nice she is. My family member also told her that it's only in movies that step mums are evil, in reality they are good and this specific woman is lovely. She wouldn't sleep so I got her to watch half a movie. She tried to sleep several times but couldn't. She think started sobbing. I kept telling her that everything will be fine. She was worried that her dad would be upset/sad if he finds out that she's anxious about his possible marriage. She cried a lot and could barely breathe. At this point the time is 1am and my whole body hurts and my family member needs to work the next day can't sleep and my younger kid can't sleep. I am trying to get the child to talk to her father so that he can reassure her and my child gets even more anxious and screams that I shouldn't make her dad sad by calling him. I get angry and at this point I am fuming and I swear at him and his abusive family and his stupidly. I spent around five mins angry and screaming. My child gets angry too. He talks to her but the child says good bye and hangs up.
I continue to feel like death and tell him that he shouldn't have told the kids such a big news on chat. He claims that he told them he's only thinking about it and it's all my fault that the kid is so anxious and it's because I shouted at him.
I just want to put this story here for your amusement. I really really hate this man. I wish him awful life. His family were incredibly awful. His brother that hit me is a bigamist (married a woman that's his son's age) while still being married to his first wife. He also beat her up so bad that he broke her leg. I am happy I am no longer part of gaff family. But I want the world to know that this kind of people exist and they maintain a facade of respectability.

First of all, has your child never met the person plans to marry?
If not, why?
Secondly your child didn’t want to speak to dad or for dad to know that they were upset, so in my opinion you betrayed their trust when you called him and told/showed him your child upset. Which of cause the feeling of betrayal would cause more upset.
It’s sometimes hard to accept when an ex especially the other parent to your children decides to move on and remarry. But the right thing to do is to be strong and don’t let your own pain affect your children or their relationship with the other parent. This is something your children will look back on as adults.

He's told them about her 4 months ago and they've met her twice. My child wanted to talk to dad but when I called she changed her mind while he was already on the phone.
Yes it's my fault for not picking up the pieces of the breakdown because he choose to tell an anxious 10 year old about his marriage in a chat. I spent five hours trying to console my child.

I have no pain to see him move on. He was deeply abusive to me and he can do whatever he wants. But to make my child upset to the point of sobbing for hours while she's on holiday with me is not what I want. This is not first time he's done this.

In my experience, 10 year old children would generally be delighted at the thought of a parent getting married - they’d ask about being a bridesmaid, having a nice dress, having a party etc. If your dd was so dramatic at the thought of her dad getting married I’d say there’s something off there.
He hasn’t actually done anything wrong. All you needed to do when she was told was to say ‘oh that’s lovely, I wonder when ‘ where the wedding will be?’ Then move on.

Your post says your child worried/anxious that her dad will be upset that she isn’t happy about the situation. Then you go on to say around 1am your friend has work next day your child upset so you’re trying to get your kid to speak to dad on phone.
How can you not be able to comfort and calm your child at home without help from friend and dad??
Like read a story, watch a movie, have some snuggles, be grateful for your time together. Kids are chill and resilient. Your kid will smile at their wedding and the smile wont be fake.
Dont mean to sound harsh. I know stuff like this is hard. But pls don’t make it hard for kids too.

How long have you been separated? Because with due respect it sounds as if you're still very much over invested in your ex. I don't mean that nasterly and I really do get it. I'm also divorced with 2 children. My ex husband was abusive towards the children and me.
I know from personal experience it takes a very long time to detach mentally. The negative emotions run high for a long long time. But realising and recognising it is half of the battle.
Once you realise it you are less emotive when dealing with shit like this!
At the beginning I think you said to him that "it's not for you to know but for the kids to know". Personally I would have just ignored this message! Not only did he then message the child which upset her but you got involved in a situation thats nothing to do with you.
Only communicate with him when necessary. Don't get involved in anything else.
You carn't stop the other parent, parenting the way they want to. Eg telling the child their thinking about getting married. But you can be the parent that's rock solid with their response. Eg "o that's nice, speak to him about when you see him next ".

OP don't beat yourself up.
Your child sounds incredibly anxious and I think that's what you need to focus on. Is she getting therapy? Or can you start doing mindfulness with her in order to help her manage her anxiety.

Your ex is a complete twat. If this is a regular thing that he winds them up when they are with you. I would limit contact when you are away with them.