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

DP backs me about it, but does think some level of roughhousing and accidents between children is normal.

Not between a 7 yo and a 2 yo. This isn't a case of your partner backing you this is a case of needing to protect your daughter.

Your step son is 7. I teach 7 year olds and I've raised 7 year olds. The reality is that he could seriously harm your daughter. What he is doing is deliberate in that he is intending to be unkind and even hurt her but he won't be aware of the serious harm he could cause. Serious harm is likely to be completely unintentional but that won't matter once the damage is done.

You can't ignore this.

From what you’ve said it does not sound unintentional at all. You need to stick to supervision 100% of the time that he’s near your DD. Has your DH asked the mum if there are any incidents like this with his other siblings? I would be looking at starting therapy for him tbh. It sounds like there’s something more going on than just sibling rivalry.

I’ve noticed in other social settings, he’s very unaware of how to interact in a friendly way and invades other children’s space - tickling them or wrestling with them when they clearly don’t want it. He doesn’t have many friends.

Is he autistic perhaps @Xante ? My DS1 def could not be trusted around his 3 year old younger brother. He loved him but just couldn't be trusted. We had to work massively on social skills with help from camhs. I couldn't leave the two of them alone for 1 minute because ds2s life depended on me always watching out. With the context you provided above it sounds like he could very well be autistic. Get him asessed (your dh should do this) and NEVER leave your dd alone with him.

Are any of the sisters he lives with his full siblings? If I am reading this right (considering there is no mention of sisters also coming to your house), this little boy cannot have spent much time with his actual father living with him. Who/where is the father of the younger sister?

His older sisters likely also come and go to their father/s. You say they dislike him - do they hurt him? Are they 'role modelling' that this is how to treat those smaller than him? Or does the father of his younger sister mistreat him when no one is looking?

His father lives with you, and yet another sister. Is he jealous of that?

It sounds as if the poor kid has never had any stability with either parent. Which is not to say that it is right that he is hurting your daughter. It sounds as if he needs some consistency and child therapy.

In the mean time, you need to never leave him alone with your daughter.

You really must stop leaving them alone in the same room together at all. Jealousy or not, it sounds dangerous and mean spirited to me.

If you go to get something then DD comes with you. Even if you just go to the toilet, she comes with you. Every time. No exceptions. End of story.

This is not normal behaviour and you are leaving her at his mercy to get injured. You are DD's parent. She relies on you to protect her. This is on you. You are her protector.

What does his father say about this behaviour OP? Is he just ignoring it, and hoping it will go away?

You have to be in same room as them at all time. Why was he alone long enough to give her bruises?

This is on you, op.

Its interesting what you say about his social skills in other settings. He definitely has behaviour problems, whether it stems from ND or a psychiatric issue needs to be explored more. I suggest someone looks into this asap and tries to help him. In the meantime you need to protect your child and keep him away from her, let them play heavily supervised and hands off or not at all.

Sounds like jealousy, have you tried giving the eldest more one to one attention.

I think pp saying stuff like 'it's just nasty' are simplifying it to much. It sounds like he has real issues and is really unhappy. Obviously number 1 is to never leave them unsupervised but I would definitely try to also dig deeper into what is actually going on with him to stand a chance of him improving. I can't imagine shouting and punishment actually helping in the long run.

Have you posted about this before? I remember the legs being squeezed?

No not normal. You can’t leave them together unsupervised.

My 2 year old sounds less violent with his 1 year old little sister - and they are like little chimpanzees constantly fighting. I can still largely trust him in the room with her for a minute (and frankly she is as violent back). It's super weird for a 7 year old to not be able to control themselves around a 2 year old.

Of course this isn't normal. I wouldn't be leaving her unsupervised when he is in the house. I mean he is dropping a two year old on concrete. Your job is to protect your daughter before she ends up with a fractured skull or a broken arm rather than worrying about fostering a relationship with your stepson. He is not a sweet boy when he is hurting a child who is so much younger than him. My sons had a lot of sibling rivalry and they had a three year age gap and while they did squabble there is no way that the older one - who had been the only child and liked it that way - would have ever done the sorts of things you mention. It's no wonder his other sisters dislike him when he behaves like this.

He knows exactly what he is doing. Your husband needs to sort it out today. Do not allow him to be alone with her, be very mindful that he is much older than her and a plan needs to be put in place to keep her safe at night.

You’ve posted this before? So it’s a long term issue that hasn’t resolved despite you having concerns over a prolonged period. This does not sound accidental and is a serious safeguarding concern.

What are you and his father now going to do to protect your DD?

Can you tackle the jealousy driving it? More 1-1 time with dad. V similar happened with relatives

It sounds like jealousy and that he struggles to find his place within either family. At his mum's house his siblings their don't want to know him and he is left out. Maybe his older sisters have treated him in a similar way.
It sounds good that DD wants to interact with him but that he lacks the skills to do so.

I would however be concerned that you are saying he is hurting her when he thinks you aren't looking and would be talking to your partner about how you are going to manage that (constant supervision, telling him you are aware of her being hurt).

You clearly think it's not normal as you are drip feeding.

Unsure why you're leaving them alone together if it's been happening for 2 years.

These examples are horrific. Deliberately dropping your dd on concrete would be enough for be to seriously question whether I’d want him anywhere near my child.

Either NEVER allow ss near your child alone, or get you and your child a long way from him. I wouldn’t want SS anywhere near my child, and it’s definitely not normal.

Jealousy may be the reason, but it’s not an excuse, and you need to put your child’s safety first. This is serious, really serious, and don’t let anyone fob you off, using excuses.

Separate now. Keep your child safe. Dad can visit at your place only without stepson.

His dad needs to have him assessed and into therapy ASAP.

I would have your child in for a physical. There might be injuries you have missed.

He's actively harming your much younger child. This will likely escalate if you don't do something now.

Re-home any pets.

Stop leaving them unattended EVEN FOR THREE MINUTES! It takes seconds to kill. One wrong punch or push and it's over.

And yes, it is deliberate. He enjoys inflicting pain. I really, really hope you don't have any pets OP.

He has a younger sister at his mum’s too who apparently hates him, and his older sisters barely tolerate him
There's a very big reason they hate him - he probably hurts them too, pinching and pulling hair is the usual go to on bigger kids. Your DD doesn't love him, it's appeasement. You are teaching her that anger and pain being inflicted is normal in a "loving" relationship. It doesn't bode well for her choice of adult partners. Protect your daughter.

This isn't play fighting. This is deliberately inflicting pain and doing it when you're not looking so he can get away with it.
I'd be extremely concerned.

Don't let your daughter out of your sight.

He is hurting her whenever he thinks you arent looking.

Stop calling it play or telling yourself he doesnt mean harm.

He may be jealous. It needs dealing with.

His dad should spend lots of time with him 1:1 and try to get to the bottom of this.