"I know him."
I'm not actually sure about that. Google translate says that "我认他" is "I recognize him"，but for most of us Chinese, we will usually say "我认识他(wo ren shi ta)" or "我认得他 (wo ren de ta)" because we're already used to it. However, some people still say "我认他(wo ren ta)". It doesn't really matter but "我认识他(wo ren shi ta)" or "我认得他 (wo ren de ta)" is recommended.
It's a cultural thing. We have a gender-neutral third-person pronoun, 他, for he/she/it. However, due to foreign influence, more "ta" were created, and some characters were repurposed to be "ta" to make translation easier.
它：Originally meaning "snake," it was repurposed to mean "it."
她：Originally being a variant of 姐 and meaning "mother" (instead of "elder sister"), it was repurposed to mean "she."
牠：Originally meaning hornless cattle, it was repurposed to mean "it (for animals)."
祂：It was created to refer to a deity. If you check the Bible in traditional Chinese, this character is the pronoun for God.