23 and 21 year old cats?!
Wow! I'd love it if my cats live that long! I have to find out what you're feeding them! So I guess it all depends on the different personalitys of the cats and Corgis. I'm pretty sure all my cats would be fine with a Corgi, just would take a little time for them to realize where they all are in the hierarchy.
Thanks alot for letting me know!