Drastic Weight Loss !!

Hello, new to the site, hoping for some input. Brother and sister around 10 years old. I say around because the vet placed them at 9 but I think they are older. My boy has been diagnosed with a thyroid tumor, surgery is recommended, but I simply don't have the funds. He is on meds which he gets as prescribed. My girl has never had an issue. Until recently, They have been moved twice, the first time was June 2018. We stayed with friends for a while. They were great ! We moved again in August 2018 and since then both of them have had a Drastic weight loss. They both seem to be my babies, same personalities, same habits... Litter box is as expected... I'm at a loss ! What can I do? There is so much more, If you want to help please respond ! Thank you !!

The weight loss could be down to many things, such as stress but a thyroid issue will cause weight loss which is difficult to regain. As long as it is under control with the medication he should be ok but will need blood tests on a regular basis. Are you able to have blood tests on his sister?

I'd bring both cats to the vet for a check up. A senior panel blood work will help determine if there is anything medically causing the weight loss in both cats, besides the known thyroid issue in the one cat.

I would also have a vet check up. Maybe talk to him about food as well? there may be a different food you can feed that would help, both with the thyroid issue and the weight ?