I've definitely heard a few cases of eg. a 2 y/o male cat mating with 2 month old kittenfoids, though that's earlier than usual. but cats grow very quickly, so they tend to have sex quite early regardless, many female kittens will go into heat at around 4 months of age
and by 6-9 months, many kittens will be considered sexually viable
cats don't really care much for age, it's not like they keep calendars jfl
fwiw I think that there is 'pedophilia' among wolves, penguins are degen af, orangutans are serial rapists, sea lions and sea otters rape babies from other species when their own female population is scarce, and some insects will have sex with larvae to impregnate them before other males can
humans have longer lifespans, tbh, so it's an odd comparison usually. most animals will not wait for 18 years before having sex jfl, many will mate before a year. some like the adactylidium mite have sex before they're even born, and many others have short lifespans and will have sex very soon.