Besides domestics what kind of cat babies are called "kittens"?

"Kittens (Old English diminutive of cat) are juvenile domesticated cats (Felis catus) that are not fully-grown.

The young of big cats are called cubs rather than kittens. Either term may be used for the young of smaller wild felids such as ocelots, caracals, and lynx, but "kitten" is usually more common for these species.

Though the term primarily refers to young cats, it can also be used when talking about the young of beavers, hedgehogs, rabbits, rats, skunks and squirrels."
https://en.wikipedia.org/wiki/Kitten

Scottish wildcat kittens are in the news today.

http://www.highlandwildlifepark.org.uk/news/article/11455/incredibly-rare-scottish-wildcat-kittens-born/

Then there are the kittens of feral cats, which may or may not be considered domestic.
https://www.animallaw.info/intro/feral-cat-legal-issues