Rufus is the youngest brother of Sylvester and Mortimer. He is last in line to the Earldom.
Rufus is the brainiac of the family, much more so than Sylvester. He's very good with devices, but not so good with people.
Near the closing of the Day That Changes Everything, he was inducted into some role inside The Spike, evidently one which gives him a very special power.
Rufus is also called Norton in the Fringes of the Basement. (Archive text for comic 4539.)