The fact that they're brothers will have no bearing on introductions at all. Animals aren't like people, in that they know their relatives. It's just like the thought that rats that are relatives won't breed with each other. Total nonsense.
Typically rats will accept other rats that are younger than themselves, but with all introductions, caution must be taken. If it were me, I'd get the intros going sooner rather than later!

Good luck!!
And when did you get so many more rats? Hehehee I guess I've missed something! I just remember your first two!
