First of all, sorry in advance for the long post (also if posted in the wrong section, I'm new to this site).
Okay let me start off by stating that technically they're my step kids and their biological mother is IMPOSSIBLE to work with in regards to what is best for the kids.
There's three kids, the youngest is 9, 10 this year, the middle child has already turned 10 and the eldest is 13.
I've known them for 3 years now but only had them living with my husband and I for a little over a year now and bit by bit I think I've made a huge difference to their behaviour and overall well being.
When I first met them they had little to no knowledge of personal hygiene (thanks to their "Mother"), they were riddled with head lice, never brushed their teeth and the eldest has always had a swearing problem (which is starting to rub off on the others but only rarely as I tend to pull them up on it whenever I am there to hear it or hear about it).
On top of all that, they have no respect for their belongings or anyone else's;
The eldest always destroys all the toys that have been bought for him as presents (or bribery from his "mother") or that he buys with pocket money, he drew on his bedside table with permanent marker and is always putting holes in the walls somehow (not with his fist, I can't figure out what with). He eats & drinks in his room when told not to and squishes some of it into the carpet and spills the drinks everywhere. He doesn't bring all of his clothes out to be washed (leaves 80% of them in his room behind drawers etc.) and leaves wet towels on the ground only to turn the carpet mouldy.
The middle child is the only one who seems to be able to show respect for belongings, his and other peoples alike. However he will cry crocodile tears when he doesn't get what he wants.
The youngest like to draw on her dolls faces, giving them a "makeover" which makes them look like Ronald McDonald, but also likes to sever the same dolls heads (this scares me a little), she also leaves wet towels on the floor and in her cupboard and can never seem to understand the concept of putting her toys (or anything for that matter) away, but other then that has come a long way, she still likes to get a bit sassy with me from time to time when shes not getting her way, likes to bring up how her mum wouldn't treat her this way. (She is her mothers favourite by the way).
When in their "mothers" care, the two youngest are treated like they sit on a pedestal and the eldest is treated horribly, he is sworn at, abused physically AND emotionally and called a lot of hurtful names, his father and I have spent a lot of time with him to help him with his confidence but his mother always ruins it by tearing him back down again.
Personally I believe they would be a hell of a lot better off without the influence of their horrible mother as I believe the sass that I get from the youngest is due to her, the middle child doesn't seem to care for his mum, only the gifts that she gives them every time she sees them and the eldest has a learning disability so he gets angry and throws a massive tantrum when he doesn't get to see but comes back in tears whenever he does see her.
I try not to discipline with anything physical as even after all this time, it still doesn't feel right to do as biologically, they're not mine to do so, so I take privileges off them or ground them accordingly and should their father see it fit to give them a smack on the bum then that's his choice, however still extremely rare.
Overall since they've been in the care of my husband and I, their personal hygiene has improved and their attitudes have improved a fair bit but still not there completely.
It's pretty much just the picking up and putting away of their belongings and respect for their belongs and other peoples that's really frustrating me, it feels like they're not listening to me and they probably aren't, how can I fix this?
Open to any and all suggestions, thank you in advance