Just seen this so just thought I'd pop in.
We have an 11 year old cat called Betty, I work from home and she follows me around like a sheep. I will be absolutely devastated when she goes but hopefully not for a long time yet! I treat her just as good as any family member, in fact she runs the bloody house lol!
21 & 23 years is bloody great lads, they must have been well looked after. Sorry for your loss, some people say 'it's only a cat or only a dog', I have no time for non animal lovers, domestic pets are very must part of any family.
Anyways, back into hibernation.