excessive thirst

Question
About 4 weeks ago, I adopted 2 siamese cross kittens (3.5 mos old) who were abandoned in a gravel pit. I got them from an animal rescue center and they were throughly examined by a vet before being put up for adoption. They were also given their first round of vaccinations and de-worming. My question is that they seem to be thirsty all the time. I fill up the water bowl 2-3 times/day atleast. The boy tends to eat much more than the girl (they are brother and sister) but other than that, they appear to be very healthy and so very affectionate! Any thoughts as to why they might be so thirsty? Thank you in advance,
Becky H.

Answer
Nothing stands out.  All of the usuals (diabetes, kidney failure, hyperthyroidism) are usually in older cats, and it would be surprising for both kittens to have these conditions.  

Fever would be a possibility, but this would usually result in lethargy and maybe reduced appetite.  And as long as their stools are normal, dehydration shouldn't otherwise be an issue.

However, I do find that my Siamese tend to take in more water than my other cats.  I always chalked it up to the fact that they're so active and muscular, their demand for water is naturally higher than less active cats with less active metabolisms.