Yeah the little one isn't aggressive at all, just scared. I've had similar with a rat I had a few years back, but when he reached about 3/4 months it calmed down, but he lived with his brother from the beginning, the fear only showed when he was introduced to other rats for play.
The cage was the hairless boys cage, but it had been soaking for a few hours, scrubbed, with new hammocks added. I replaced all the food bottles too. I have another one of these cages that hasn't been assembled yet, which is for my females to move into when the babies are gone, I might try using that incase I did leave some scent behind.
In that case, I'll try the vanilla tonight, see what happens.
He has a lot of hiding places, and the hairless gets confused when he can't fit in there with him. There's definitely bolt holes for the little one to run to, but I don't want him to just hide all day and only leave to eat or drink, as they'll just never get along
I'll look into making one over the next few days.
I'm not really new to rats, I got into them about 5 years ago when I did weekly work experience at a zoo with hairless ones. I got my own shortly after and have had them since. This was my first attempt at breeding though, so I'm new to that. I'm definitely new to introductions though, I've always just bought whole groups at one time until recently.
I'll have a look there, thanks x