Hi
Dp has a 3 year old son. I have 2 children. I'm writing on here because I'm really struggling to deal with dps relationship with this ex. It's absolutely toxic and it's getting to the point where I've had enough.
Last night dp dropped his ds off and came home absolutely fuming because his ex has said she's going to csa. This has all stated because she won't let dp have their son at any point over Christmas Day.
Now I dislike his ex. She stops dp from having dss whenever she likes - for no reason. She will book trips away on the weekend he's meant to be with us. She will refuse to come and pick him up when it's her turn. She will demand with we have dss whenever she wants so she can go out - which we don't mind as we absolutely love having him obviously.
Lately this has been going on a lot. We had booked a family day out to see santa next weekend which has been booked for months. She's always known about it. She's not said dss cannot go because she's doing something with him.
We had started having dss one night through the week and she's put a stop on that too because she wants to go out on that night and she 'cannot be arsed to drop him off as she won't have time to get ready' so she will just 'give him to a mare instead' 
So yeah I don't like her much.
There is always arguments between them both constantly but last night was just enough for me.
To be fair my dp doesn't pay weekly maintenance. He pays her a lump sum every couple of months - about £300. However the last month he didn't pay anything as he's well and truly sick of her messing him around. She's now threatened csa. He's come back at her saying if she does, he's going to report her to HMRC for getting about £600 a week cash in hand. She works part time but then works pretty much every night in a bar where she gets £100 a night cash plus tips.
Honestly they are both as bad as each other. I'm 33 years old now and I do not want to get involved in childish behaviour which is what this is.
I'm on my dps side. I really am but when I hear the way he speaks to her it makes my blood boil. I cannot stand her either but she's still the mother of his son.
I don't see this ever being resolved. I don't see it ever being amicable. They need to put something in place for dss - maintenance and a set time when dp has dss. I've suggested they get someone to act as a middle person so they don't have to speak. He suggested her sister and said that would be a good idea. But what's he done first thing morning?? Rang up the ex and had an argument with her. I'm so sick of it. I can't stand my own ex. He did some horrible things to me etc but I will always be civil to him as he's my children's dad and I cannot change that. We never name call, give threats etc which is what these 2 do.
I know it's not my place to get involved in all this and I'm not involved as such. But last night we spent hours arguing about it and it's doing my head in.