
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.