2 year old and 3 year old behaviour out of control! Desperate need of help!

[Louisee58]

I have a 3 year old son, soon to be 4, who is very well behaved, very polite, calm and just generally a nice child to be around he is very loving, my 2 nephews on the other hand have my sister at her wits end, and my mum who is doing all she can to help my sister stay a float! my sister is a single parent and my 2 nephews, who are only 15 months apart, are 2 and 3, are the total opposite to my son. They both have very bold personalities and need to be entertained constantly, but find it really hard to do as they are told. They eat well, but after every meal the hoover has to come out as they just throw food everywhere, the 2 yo used to sleep great but lately has just decided he's not going near his cot, changed it into the bed but still didn't help now he doesn't sleep, the 3 yo has taken a long time to potty train, finally done it, and now just stopped again, we think maybe because he sees his younger brother getting his nappy changed? I know most children revert back for a little while when potty training, as did my son, but my nephew seems to have just given up completely!
Both of them climb out of their car seats, my sister who lives a 5 minute drive away from my mums can take up to half an hour to get home as she has to keep stopping and strapping them back in. This morning, the youngest actually managed to get out of the locked car and run down a busy street before my sister could catch up with him, meaning she had to leave the other one in the car alone, who could have done the same thing in the opposite direction, its getting to the point were it is really dangerous now! is there any type of restraints we could get that would help secure them better in their seats? Obviously the doors are child locked we don't know how they manage it!
We have tried the naughty step, obviously not for long enough, as neither of them seemed to take any interest! when my sister tells them off, she does raise her voice and shouts, to which they just shout back, I know from experience with my own son, lowering the tone of my voice is much more effective, which I have tried with my nephews, but just get completely ignored.
We just don't know where to go next, does anybody have contact information for a super nanny/nanny 911 type of person? It got to that point now! they cant be taken into the shops they just run riot, climb out of the trolley, fight etc. Neither of them can be taken anywhere with the family for, say a meal for an occasion, as its just too hard! we have days sometimes were we will spend the whole day together, but not actually say a word to each other as we will be sorting the children out the whole time! When they aren't behaving like this, they are the sweetest boys, really funny vibrant personalities, but this is very rare!

[MrsWinnibago]

What is their diet like? Do they eat much processed foods? Stuff with additives? Squash?

[Louisee58]

No they are actually really good at eating, they love water and milk before anything else, pasta, cheese, etc they eat what we eat to be honest. They used to snack a lot which my sister has stopped now, and they eat a full plate full at meal times. I would have thought the same thing otherwise.

[melonribena]

It sounds really hard for your sister. Do they go to nursery or groups at all? That would help their socialisation.

[YouHaveBeenOutbid]

We got one of these for the carseat which has been great but the reviews are mixed with some saying the kids worked out how to undo them pretty quickly:
www.amazon.co.uk/Houdini-Stop-Houdini1/dp/B0044VUXGW?tag=mumsnet&ascsubtag=mnforum-21

[Louisee58]

Thanks, I ordered them yesterday, but the problem isn't them taking their arms out, they can actually undo the buckle, they are real life houdinis lol

yes they have both been going to a nursery 2 days a week as my sister works too, since they were both 9 months old, the oldest will be starting school nursery in the next 2 weeks, really hoping that will have a massive impact on him as its a lot more structured than the nursery he was in. The oldest one seems to be calming down as he is getting older, so hopefully it will continue and the younger one will follow suit, but its so hard at the minute, my little boy will play with them for a few minutes, get hurt and say he doesn't want to play anymore, which is understandable but heart breaking for my sister to hear, they don't get away with it so I don't understand.

Even spending a full day at the park or going for a walk etc doesn't calm them down, they are manic in the park and it continues when they get home, and neither of them sleep either.

sounds like a strange one and probably wont make a difference but both of them drink a lot of milk, think this could have any effect on their behaviour?