Whiskers, my sister's cat, died peacefully in his sleep today. He was mauled by a dog a couple of years ago, made a good recovery from that but was generally fairly poorly for the last few months and fairly obviously senile, so it didn't come as a huge surprise. His sister died in much the same way last year.
Whiskers wasn't the brightest or friendliest of cats, but people liked him, and he was an expert scrounger which probably didn't do much to keep him healthy - half the street seemed to be feeding him sometimes. He was definitely a character, and he'll be missed.
PS - please don't offer kittens. At the moment they're not planning to get another cat, although I suspect they will in the end, and I think they'd rather make a decision in their own time.