I've got two kids, roughly the same age as your niece and nephew. For a while I thought along the same lines as you, and was perpetually trying to find ways to distract one so the other has room to grow. It took some hard lessons, and looking around and seeing other people struggling with similar difficulties; what i eventually figured out is that we tend to underestimate what the younger child is capable of because we tend to see them through the lens of "older vs younger".

Once i got rid of that lens, I was just about shocked to see how hard my youngest pushes himself to do the things his older sister is doing. He's doing things now that my daughter at the same age wasn't able to; and I wonder how much of that is a function of her capabilities vs limitations I imposed on her based on a series of assumptions.

My advice to you, don't differentiate too much; you'll be very much surprised by what the little one is capable of. It WILL take more than an attempt or two, but if you're able to stick through and watch how your nephew behaves you'll most likely notice some mimicry and very concerted attempts to be able to do what his older sister is doing. Sometimes he'll be successful and they'll both play/do the thing together. Other times, he's won't, he'll get frustrated, then he may act out; and on some occasions he'll just get bored and this is where you'll need to do some entertaining for a few minutes so he doesn't go right to his sister to try and get her to stop doing the thing he can't do (yet).

The side benefit of this is that once established, you'll be able to dedicate one-on-one time to each as you see fit without feelings of unfairness or one feeling left out. In essence, don't hold him back; pull him along and he'll push himself forward to match his sister.

Kids are people too, drunk people, but people none the less.

The niece is really good about finding ways to entertain herself and the nephew will always try and take it for himself and intrude, usually not in a compromising sort of way. Obviously, this is pretty typical kid behavior overall.

I think this is your core problem, really. Who is policing your younger nephew's behavior in this regard? Even at that age, being able to accept limits without losing your temper is important. Maybe offering him an alternative activity as a distraction would help? Younger siblings often want to be involved in whatever their older sibling is doing, so there's an element of normalcy to your nephew's behavior certainly, but it's also not acceptable and that needs to be communicated clearly to him. He needs to have ways to entertain himself when his big sister isn't available or at the very least learn to not take over any activity she engages in.

A 3 year old needs structured play so you have two choices here, firstly find a seperate adult to do the things the younger child needs, or secondly you can do the same activity but tier it. So say you want to teach the older child to paint with watercolours, that's cool, get the younger one some paints too but they aren't learning techniques but maybe being given a colouring page and working on painting between the lines.

Maybe the older one wants to play pokemon, get the little one an age appropriate game or interactive story on the ipad and help them both.

There's basically 2 options, distract the younger kid with activities while playing games with the older kid, or let them play with you and help them a bit more. Both can be appropriate at times.

The way I handled this with my young siblings, was hand them a game controller unplugged.

schedule separate activity times to individualize the activities

This is exactly what I do with my kids. Each of them gets a scheduled block of "choice time" with me to do whatever they like. When one kid's time it up I say, "Thanks for playing with me, but it's time to give X their choice time" and promptly move to the next kid. The quickly learn that they will get a turn, and they don't like their own turn being interrupted, so they respect each other's time blocks. I haven't found another method that works well, at least in our family.

It's important that you set expectations in advance and be consistent. If you run too long with one kid and give less time to the next kid they will immediately recognize the unfairness.

Why can't Parent1 do something with them seperately thats age-appropriate and ditto for Parent2, why do they have to be in the same room/physical space necessarily all the time, I don't really get this.

My younger bro wanted to be involved but he knew he had to accelerate his learning cuz I wasn't waiting for his 2-years-my-junior ass lol

Hell, we're both grown-ass adults and the hierarchy STILL remains intact 😉

Your niece will probably brag to your nephew about the cool thing that she did, and rub it in that he was too young. That’s what siblings do. This is especially true if he’s ruined things in the past, and she’s harboring some resentment, which she almost certainly is.

I agree that it’s unfair to hold her back, but being left out and being forgotten are two very different things. Spend quality time with him, niece excluded, doing an activity that he will enjoy, or that he has chosen.

It is not your place to make such decisions. Harsh, but their parents have the final say. Therefore, talk with the parents if you wish, but be advised that they might take it the wrong way.

Also how does he feel about "girl" stuff aha?

Watch Bluey. They’ll like it, and you’ll learn a few things too. There is also a board game and a mobile game.