Difficult 3 year old

[FJR1008]

Hi, any words of wisdom from anyone?
My highly sensitive just turned 3 year old is hard work!! He's always been emotional/grumpy, especially so since his sister arrived 6 months ago.
He doesn't particularly like other children his own age, and it comes out through grumpiness/pushiness when around them. I think he is completely overwhelmed in this situations, and even though his speech is good.. it's like he doesn't know how to communicate with children his own age. Everything is 'mine', or gets angry when the child even tries talking to him. He is still fairly reliant on his nap, and is starting pre school 2 days a week tomorrow (9-3). Anyone have experience of this and tell me it gets easier?
I've tried the firm mum, I've tried the soft mum. Nothing particularly works, I can see he doesn't understand or mean his behavior, he just doesn't know what to do in these situations. Thanks.

My oldest is 3 as well so i can't speak for older children but I always find the things that help toddlers/preschoolers with managing behaviour are:

Consistency and routine (they don't understand much about the world so routine helps them to know what to expect and makes them feel secure)

Limited screentime (apparently it can make behaviour worse and have noticed this in my own children)

Being firm with boundaries (no always means no, of you're consistent they don't challenge you as much and it reduces tantrums)

Providing alternative behaviours (e.g. if they push sibling because sibling has taken their toy, I would direct them to move into another room or to find the sibling a different toy)

Making sure they're having a nap if they need one as well. My 3 year isn't quite ready to drop her nap and if she doesn't have it, behaviour is a lot worse.

It might also be an adjustment because of the sibling (Im sure when my second was born it took quite a few months for the older one to adjust, and they might have to re adjust when baby learns new skills like crawling and grabbing things)

I also think a lot of this behaviour isn't necessarily problematic but developmentally normal, like not being able to communicate well with children his age or feelings overwhelmed sometimes.

But I am not an expert, these are just my thoughts and you will have better insight into your own situation than me.

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