Being badmouthed to the kids by ex

[DontMissHisJowls]

I'm sure this has been asked before. I've been through a very painful and traumatic split from my ex quite recently - lies, an affair on his part and then being totally blamed for everything with a complete rewrite of our history. Things weren't good at the end but there were happy times and this was all a huge shock to me.
Anyway, my eldest, 11y, has many questions and a lot of anger. He knows about my ex's affair - my ex even told him her name - and will often blow up when he stays there. I haven't bad mouthed my ex at all but have had lots of difficult questions to me too which I've tried to respond to in an age appropriate way. I also have a younger child who is 8.
Today the kids have come back to me and I have heard that their dad told them that our marriage was awful for years, that he wanted to leave but only stayed for them, that I made him feel unwelcome and he had to leave.
I hate hearing this but more than that, I can't believe he has said all this to 2 innocent boys who have many good memories of their parents, and now that has been shattered. My eldest is angry with me and won't talk. My youngest is sad.
I just don't understand how he can justify doing this to his kids. He has tried to justify it and said many more hurtful things to me in the process.
What can I do? I have tried to support my kids and explain that there were many good times and that not everything was bad, and that neither me or their dad was perfect and we hurt/annoyed each other at times, like all married people do. But I can't help feeling that my ex has tried to put the blame on me with my kids now. I can live with him saying those things to other adults, even our mutual friends, but to do this to kids is unforgivable. I'm so angry and sad for my kids who were making good progress in getting through this. Now I feel we are back to square one and they are being put in the middle to save his ego and pride, a middle aged man who should know better.
How do I deal with this?

Communication and not in an uncomfortable place. So I do it sometimes in the car that way their isn't to much forced eye contact and it's more relaxed. Sometimes one on one sometimes together.
I had this recently with my dm saying things to the ds and they seemed different with me. It was because they didn't want to hear the stuff and it cause them upset.
I said that I had notice they seemed upset and asked them to tell me anything that was on their minds, or if they wanted to ask me anything.
I then explained, you know me, you know how I am with you, you know that when people don't like each other bad words or things are said. When you fight with each other you do or say un nice things because your hurt.
I explained that beside me not speaking to their nan because of her actions I don't believe you should be involved in the argument and I don't expect you to pick sides Infact I've made sure not to tell you or say bad things.
I told them the hurt she has caused me isn't something I will expect but as your nan she loves you and you have a right to still have a relationship.

If the other people continue you be cruel or hurtful you do not join in or add to it, never over explain what happened they don't care and can't process all of it. Remind them they were they and most part the relationship had been happy but at times you do have issues just like they do with their friends or siblings.
Good luck Op

@stuckbetweenlife Thanks, that sounds like good advice. The kids are better this morning and things feel more normal but if he continues to do this I would worry. Have been reading about parental alienation and will probably speak to my solicitor about this if it carries on as it is damaging for the kids. I can cope with his comments as an adult, even though I don't like it, but they can't. I hate not being able to protect them from this.

Can you just message him and just say very clearly an as short as poss yo please not badmouth me because i do not do to you. Our children should respect us. And we should be a lesson that although things dont work out ypu can still be civil and grown up.