Welcome to the forum cfrabbitry04, the first thing to do is bring your senior kitty into the vet for a full exam, geriatric blood panel including T4 Thyroid check and a urinalysis. Once the test results come back, you will know more about what is going on with the health of your boy, you can then decide about treatments if necessary.
The weight loss is common with a number of health issues, could also be normal age related for a senior. Increasing the canned food and adding some extra protein like cooked or raw chicken breast is always a good idea. For a male cat, especially, it is important to limit or completely remove, if possible, the dry food without reducing the amount he is eating. A high quality meat protein based food that has no grain, corn or filler will be greatly beneficial to preserving his health. Male cats are at higher risk of urinary tract issues and dry food puts cats into a state of dehydration which is why drinking water & having extra moisture in the form of canned/raw food is very important.
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