I think it's a shame that he had to go to court, but I also feel that it's a little unfair to have to pay thousands in medical bills because a cat bit you!
The sister had a responsibility to keep the cat away from people if it were a cat that bites. Same with dogs who bite. The brother had a responsibility not to let his bite get so out of hand that he required thousands of dollars worth of medical treatment to fix it.
I'd imagine the court ruling also took into consideration loss of income from being hospitalised, but it's a LOT of money.
In Australia, at least, impairment and disability assessments are based upon part-of-body impairment or percentage of whole body impairment, and a set sum is allocated. Therefore, his hand may have been 20% impaired which led to an equivalent assessment of, say, 5% whole body impairment, for which the payout would be `set' amount of dollars. But that may not be the same where this happened, and once lawyers get involved then the sums can vary hugely.
All-in-all, I think that it should have been treated the same way dog bites are. Obviously it was a serious injury in the end, and he should have had his medical bills paid and his loss of income recompensed. Whether that came close to what he actually got paid, well, I guess we'll never know!
I think the bottom line is that people need to be responsible for their animals if they are known to be aggressive - cat, dog, horse, bird, rat - whatever. And if you are warned that an animal is aggressive, you stay away from it! I think this is one of those situations for which there are definitely `two sides'.