Just a suggestion but Rats become better with owners and visitors alike if they have one of thier own living with them.Your brother really needs to have a companion for his little rat.Rats are real cheap like 5.00 to 7.00 dollars and you could make the rat more happy and im sure your brother would be happy to find another furry friend when he returned.
Just make sure they are of the same sex,so you dont have babies or fighting.You will see a huge diffrence.Rats get bored and lonely and when they dont have another rat to play with ,and they react better to humans when they are in pairs.Imagine being stuck in a cage and your human companion only droped in once in awile or even twice a day isnt much in a 24 hour time.Youd be very lonely and bored out your mind,Rats are night owls,thats when they are most active and im sure most people are asleep by then.Its really cruel to keep only one rat.
I hope you will look into this and maybe get in touch with your brother and see if he is okay with it,it could be alot of fun to watch and everyone would benifit in the long run. I ahve included some web sites so if you would like to look up any imformation on introducing a new friend or basic care or things that happen when an owner leaves or any concerns,it has loads of imformation about Rats. Good luck with your little visitor and truley think about buying him a friend..