[Nikkigrace]

I would get them into something bigger asap to be honest. Lack of space could also cause them to started disagreeing and fighting. I wouldn't even leave them in it a week or two like you said if you can help it. They will still get used to each other and you can still start taming in something bigger.

I'm not familiar with the rabbit cage you mention but it seems similar dimensions to a zz2 which is what I keep my trio in and what I would suggest you use for your 4 if you can?

If you haven't sexed robos before then it can be VERY difficult to determine whether they are male or female, so I would strongly recommend getting a vet to sex them for you ASAP as they are already at an age where they can mate. Or post photos on this thread and people can help you out, but I realise they might not be keen on being handled yet. If you can scruff them and take photos then I'd do so. You don't want them mating as I said earlier, firstly they are siblings and secondly they are very young.