Yes, that would be - Znáš ho také? or when emphasizing "him" Znáš také jeho? Jeho znáš také?
Masculine pronoun has two forms depending on whether the pronoun is emphasized or not, feminine pronoun only one form "ji".
If it's a neutral sentence, the pronoun "him" is in clitical 2nd position and you use the short form "ho". When emphasizing the pronoun, you'll move it at the beginning or at the end and use the long form "jeho".
"Také" is an adverb, and you'll like adverbs, because they never get declined or conjugated. Instead of "také", in spoken language, you'll often hear "taky". It's another form of the same adverb.