In my opinion, getting two this close together from the same breeder and where the two kits were in the same room with each other should not be a problem with quarantine time ... UNLESS the breeder has had a illness or problem with any of the chins it that room between the time you picked up the first one and the time you pick up the new one.
There is the introduction time that needs to be considered. Kits tend to get along better ... usually ... but not always. I have known of litter mates that fought in the first 3 days. Make sure you have a second person handy and that they are introduced outside of the cage ... in a small area. Do not leave them alone inside the cage until you are sure they are getting along good. Stay within hearing distance for the first 24 hours and be prepaired to separate them if necessary. Usually there is not a problem, but there is always a chance their could be a problem.
Basic rules:
If they sniff each other and snuggle or play ... it's almost a given that they will get along.
If they ignore each other ... it's a good chance they will get along.
If one or both become aggressive instantly ... more than likely they will never get along.
I may sound overcautious, but if you ever find one after a fight, you will be, too.
Jo Ann