To think 7yo deliberately hurting 2yo is not normal?

Yes I would be worried and I wouldn’t be leaving them unsupervised for the foreseeable.

By the sounds of it he doesn’t have any good sibling relationships at all so he probably doesn’t understand how to actually build one. How often do you and DP spend quality time with him? From what you have said you are constantly shouting at him so that probably isn’t helping either. Apparently even negative attention makes children feel good so if the only way he is getting attention from you both is by hurting his sister he will keep doing it.

I think you need to teach him how to actually play with your daughter. My 5 year old has been a bit rough with my 8 month old the last couple of months (not the extend of squeezing legs until they bruised etc) but still too rough for a baby. I’ve taken lots of time to sit with him and my baby and show him how I want him to play and given him some toys that are just his to play with his brother. You could get them both to ask the other to play something of their choice and set a timer for 15 minutes before swapping to the others choice. You could introduce star charts and reward them both every time they play nicely, with a treat when they reach 10 stars?.

I’ve also make an effort to take both of the children out separately and come back with a small gift from one child to another. Obviously I pick the present from the baby to my eldest but my eldest loves it. Could you do similar with them both?

I think you need to build their relationship up for it to stop. I would bet he is a young boy who gets absolutely no quality time with anyone and is lashing out in the wrong way as it’s the only way people notice him.

It sounds like you are more involved with your step children, than their own father is OP. It's wonderful if you are able to have a good relationship with them all as a step Mum, but not at the expense of your own daughter. Does your DH often leave his other children in your care, or is he always with them playing and talking with them when they visit?

The more I read the more I feel quite sorry for him. But I know if it were my child I wouldn't have the patience for him either !

Some schools access counselling services, or cahms, could you speak to the teacher again about those pathways?

Do you talk about it ever when it's not happening ? Just wondering what he says ? Is he quite an angry child generally ? he sounds very much like a child who wants attention and doesn't care if it's positive or not.

That's a disgusting thing to say .

This really sounds like ADHD/ ASD struggling with cues and impulse control. Wanting to play. But also being jealous.

If school share your concerns - then I suspect you are correct in your read of the situation RE ADHD.

To me it feels like he is very much the odd one out and never has had much social interaction.
His two older sisters would have had each other for company. He then came along after a gap so would have been younger and therefore not into the same things at the same time. He may also possibly have been born as an attempt between his parents to repair a fractured relationship, but instead it didn't. If his mum and dad then separated maybe they had less emotional energy to deal with him.
Both parents then meet someone else and both go on to have new babies. Again he is left out of that as he isn't in either house full time and once again there is a gap, so not real sibling of the same age to buddy up with like his older sisters have.

I feel very much like family dynamics haven't helped him, and while maybe there is ND there, the situation he is in doesn't help.
Can you get him any external support?

Does he do the tickling / invading space with other kids his own age or just his sisters? If it's just his sisters then it's probably a family dynamics problem. If it's all the kids he plays with to the point where he doesn't have friends then it could be something innate. He really needs some help, for his own sake and for the rest of the family especially your DD.

How much older are they? Can't they be encouraged to play with him? It sounded like he came alone and was just with your DD, not that you have SS, two SD and DD in your house.

So do the older sisters come too to your house? If they are his full sisters then that means your partner is their dad too??

Wow some of these comments are a bit shocking about a 7 year old child tbh.
Definitely do not leave them alone unsupervised.
DSS sounds jealous. He’s a child from what sounds like a chaotic home.
Tell him off and don’t let there be another opportunity again.

I wouldn’t be leaving her out of my sight in his presence. I would also be very clear with your DH that this stops or you will need to be elsewhere with DD when he visits as this is a child protection issue. Get your DH to do the parenting and act like her mother!

You and DH need to separate the two kids and to watch like a hawk all the time when they are together. Your DH needs to step up. He doesn't go outside for a cigarette while his children are playing. He watches and protects his daughter.

7 year olds don't normally roughhouse with 2 year olds. If invading other children's space is your step-son's usual way of playing with kids all ages then he may well have some kind of innate problem. Could be a few things but autism fits your description quite neatly. Your DH needs to get help to find out what the underlying problem is and how to help his son. He's the Dad and if his ex is in denial then it's his job.

Thanks. It wasn't clear from your earlier posts that all of them come to you. It sounded as if it was just him. So, not quite as chaotic as I was reading.
Their father needs to do more to teach them all that you don't bully, and especially not someone smaller than you. If the older ones are unkind to him, it really isn't all that surprising that he has learned to treat others thos way.

You said on your previous thread that you and your partner had agreed one be responsible for one child each and not to let them interact without one of you being there supervising. What happened to that?

You've let this go on for over a year now.

He’s done it again today

Your young kid is being abused in your home.

What are you going to do when he leaves more marks or serious injuries and you and your partner get flagged as possible child abusers? Have you followed any of the previous advice to have him assessed? Kicking the can down the road won't help your daughter here.

So you know he hurts her yet left them alone together because dh getting a smoke was more important. The priority is clear and messed up! A 7yo won’t care about docked allowance so that’s pointless as a punishment. I do think we read it a lot when parents move on and create their “perfect” second family, the dc from the first attempt that failed are seriously affected but expected to get on with it and be happy for the grown ups having new babies with new partners.

I would not hesitate to remove that nasty little shit from my life, personally. Why should your daughter have to put up with him? You are not safeguarding her.

I would say more sociopath describes his behaviour. Whether it is or not a qualified expert would need to assess.
But it is not okay. OP please look up sociopaths in childhood.
And get qualified help.
And I would not accept roughhousing between a 7 year old boy and a 2 year old girl should be considered normal either.
Your DH has a role to play here. And that roughhousing is okay approach is not alright at all.
Please get help. DH or not.