To think it’s not normal for kids to fight like this?

Would you ask her preference? She’s old enough to understand that she can take a toy to her room for a bit of time without her brother. I’m not suggesting banishment. Just that offering her this option might be kind or start a useful conversation. She might prefer to be with her brother and be harassed!

I have 2 sons, 13 and 11 and a daughter who is 8 and they cannot keep their hands off each other, constantly wrestling about together and have done for as long as I can remember. They love it and are all equally invested in the antics.

They never deliberately hurt each other but it usually ends with my daughter crying but she is still always up for it the next time. I just leave them too it as they are having fun and off a screen 🤣. I keep on wondering when they will give it up as the 13 year old is definitely getting too big for it!

He’s after attention! That’s perfectly normal at 3. if you had two boys (I do) the elder would probably be fine rough housing. Your daughter isn’t. You need to protect her.
i would take my younger one to the loo with me if I knew he’d wind up my eldest. Had a long time when this was the case. My eldest always has a safe space in his room when ds2 is being annoying. I’m not sure why a five year old can’t play alone in her room if she wants to.

You’ve done well to spot the dynamic. Most important step!

Mine were the same at that age (same age gap & girl/ boy combo) I remember thinking that it was just non-stop winding each other up and constant fighting. It got much easier as they got older and the physical fighting stopped once my son realised he was much stronger than his big sister. They are young adults now and are really good friends. Hang in there.

I used to barrel in in support of my poor little baby, until I walked past the room and saw baby ds2 standing in front of the tv, looking over his shoulder and waggling his nappy clad bottom at DS1 who was just trying to watch a programme. Little wind up merchant, he was.

So it’s probably a kind of attention seeking because he loves DD and wants her to play with him. If she knows that’s why he’s doing it she’ll be more patient, and he’ll learn better ways to get attention.

Stopping him winding up his sister is more important than housework if any kind. He’s at a stage. You need to work through it, the same way you did potty training.
It will repay the time and effort many times over.

Also teach your DD skills to nip it in the bud too, and back her up. So she holds her hand out and shouts STOP, with a scowly face. You immediately pop up and remove him, unless he’s already backed off.

I had the same problem. I do understand. Mine (adults) are awesome friends now, from stalwart enemies.

My b/g twins used to be like this. Absolutely horrendous, nothing I could do to stop them! Luckily the passing of time happened, and it faded out around 4.5/5ish. They’ll still have the odd scrap, but nothing like it was and it’s mainly for fun. Not terribly helpful of me I know…!

I think it might be the rough playing with DH that's encouraging this behaviour. Am not saying there's anything wrong with it, but a friend of ours used to pop over for a cuppa and he was really tough and tumble with the kids. I noticed after he had gone the kids were quite wound up

You need an activity that will give him the stimulation he needs without involving his sister.

I spent hours - and I mean hours - freezing in parks to let the kids run about. We also have a swing ball now they are older. Climbing, swinging, hitting, running. Any of that you can facilitate at home?? Easier in the summer, I know.

it seems abnormal that they can’t be left unsupervised

It is but until they have secure boundaries they cannot.

You need to stamp on it hard.

The older one needs to stop winding the little one up and the younger has to be told firmly no hitting or fighting.

A very firm sharp ‘NO’ EVERY time and separated and sent to a different part of the room plus lots of praise for good behaviour and positive reinforcement.

Try to facilitate short bouts of nice play between them then praise them and reward them when it goes well.

There needs to be value in behaving nicely and treating each other well.

I’ve seen so many parents not deal with this sort of stuff and it escalates and ruins the potential of a good relationship during childhood.

I am talking from experience in my own childhood. My own children are unusual and literally never fight but both have ASD so their interactions are atypical.

Stop with all the waffle about kind boys and kind hands - a 3 year old doesn't have the capacity to assimilate verbal information. A simple 'no hitting' and remove him from the situation is enough. Make him come to the kitchen or bathroom or wherever you are if he won't leave his sister alone. Don't encourage rough housing and play fighting with DH either, it's giving your little one mixed messages.

i remove him and remind him he’s a kind boy, and kind boys listen when someone says stop, and kind boys use kind hands and gentle actions. Etc. It’s made some impact but what else can I do?

This isn’t working. Because - to put it bluntly - he’s now obviously not trying to be a kind boy and is trying to wind up his sister. (This is the sort of behaviour that has gone on for time immemorial, that said! This is kids!) So I would just take a firmer, no nonsense approach- along the lines of “I know what you’re doing - stop it or there will be consequences”. And then follow through on that. I’m sure he’ll soon get the message that it’s not worth the flak. (Same with your DD if she’s the one causing the fights, of course).

Mine physically fight when they’re bored. It’s weird, it’s like a form of entertainment. They also verbally wind each other up when they’re bored. It’s exhausting, I don’t know how to solve it as boredom is part of life and I can’t be providing them with constant ‘fun’ to stop them arguing! Sorry not to be able to help, but just putting ‘boredom’ out there as a potential trigger!