I have 3 male cats one that is 17 yrs old one that is 9 yrs old and a 2 month ole. My 9 yr old is an outside cat and the other 2 are inside both the inside cats urine smells of ammonia they drink plenty of fresh water and eat frisky indoors dry food. My 9 yr old eats the same food but his urine does not smell. What do I need to give or do for my 2 inside cats to help the smell of their urine.

Are all three neutered?

Cat urine always smells like ammonia, but some can smell more strongly than others. Two months is a bit young for it to be a hormone issue, but getting him fixed might help.

Dehydration can cause a stronger smell. It's possible he just doesn't drink as much water as the others. At that age, many kittens still nurse on occasion. Feeding him wet food (if you don't, already), or even supplementing his water with a small dish of kitten milk, might get more liquid into his diet.