are you sure your ex isn't saying things infront of him about you? there could also be a little bit of jealousy as your other child is with you all the time. we went through this with my step daughter. she would do naughty things (which iwould catch her doing) and then get the blame put onto our son ( her half brother) in the end we realised it was jealousy, so now dp tries to spend a bit of time with her one to one and the kids get on great now. dont know what else to say really hth?

.....generally acting as a near-3yr old should be. My eldest is and always has been a growing concern and i'm concerned the less he see's us the worse his situation is going to get.

Hello, This is Salsta’s partner Alex.
I have a 6yr old Son from a previous relationship, and he has always been of some great concern to me and Salsta my partner for 4 years. My Son is distant, introvert and moody. My youngest gets very excited when his older brother comes to stay, as he’s only 2 he doesn’t really understand he’s annoying his older brother. Recently my eldest has been getting upset when i pick him up saying he doesn’t like our youngest and that he doesn’t want to stay the night. My Ex keeps asking him "Are you sure you want to stay with Daddy" in front of me whenever i pick him up. She makes such an issue of it lately he then starts to get upset.
I was called up the school this week where i was told he recently drew on another childs jumper, is generally distant and not concerntrating and he is falling behind with his work. The head teacher said she had spoken to him and his only concern was staying at ours at the weekend.
My Ex recently took him on holiday, i didn’t see him for 3 weeks, so i asked her if during her holiday she could find the time to ring me so i could speak to him. I didn’t get a call at all during his holiday. He told me he spent most of his holiday in a kids club and not realy with his Mum. When he came back his finger nails were very long and very dirty, its kind of down to me to keep him clean. He started school without his hair being cut and his nails in a terrible state. When my Ex works my Son goes to a kids club called cosmic club above his local shops. Her partners Auntie looks after him or her step-sisters grandmother (she had a child when i met her by another fella) or members of her family have him. I was told a few months ago by my ex that he feels pushed from pillar to post by coming to stay with us. I am told its important i listen to him if he says he doesn’t want to stay, by both her and his headteacher. He has also said to his teacher he doesn’t like going to "cosmic club" but his mum says she won’t listen to that and that its important he keeps going to cosmic club.
Whenever i pick him up he is on his playstation. When he was 4 he was playing Grand Theft Auto, which i strongly opposed and she eventually stopped him playing. Whenever i phone he is on his playstaion. When i asked him why he doesn’t want to stay the night with us he said its because we don’t have the "Wall-E" game and his mum does. HIs mum doesn’t take him to activities, whereas i take him to kickboxing and trying my best to arrange for her to get him enrolled in a football team. The headteacher agreed with me that he needs to get out, learn new things and interact with other children to help build his confidence. I took him home early last night because i made the mistake of asking him directly if he wants to stay, which in future i think instead of asking directly i will just see if he causes a fuss without anything being said to him. His mum said at the door that it will work to my advantage and i should tell him i have the new star wars game to persuade him to stay, when i said "But i don’t?" she said "well he doesn’t know that". She said it was important he continued to go to his cosmic club, and i said "its important he see’s his Dad regularly" which seemed to get lost in translation.
I am considering taking him to see a child Psychologist (sp) to see if they can give me some advice, maybe even a solicitor to concrete the times he visits me at weekends. I am the structure in his life, we teach him manners, he speaks like a teenager with such an attitude at times, but it feels like all the work we do at weekends then gets lost when he goes home and is shoved in front of the Playstation.
I feel  like an awful Dad, but i know i’m not. Our youngest is a bright young man we always get compliment