Hekyll and Jekyll? J/K. They have such similar markings that I'm assuming they're brother and sister (that and their age), such cute kitters. Your boy looks so much like a kitty we had many years ago that we named "Spice" because of her coloring, but that doesn't quite seem to fit for a Tom.
For your "Red", I suggest Butterscotch, "Butters" for short (yes, Southpark fan here!). For your "Grey", I suggest Dutchess. One of our girls we had to euthanize a few years ago was "Dutchess" (weirdly, she looked exactly like Dutchess in the movie "Babe"). Grey seems ladylike in the pic's, I love the one with Red laying on her where her little paws are tucked into her chest..
I think calling "Butter's and Dutch" for your fur babies sounds like a cool pairing of names.
Alternately, "Bubble and Squeak"?
