People you know very well, but who aren’t related to you.
Your kith are the people you know very well, but who aren’t related to you. If you’re asking all of your best friends over for dinner, you can say that you’re inviting your kith.
It’s very rare to see the word kith unless it’s accompanied by the word kin, or “relations.” The phrase “kith and kin” means “friends and family.” If every actor in your local community theater’s production of “The Sound of Music” invites his or her kith and kin, the seats will be full on opening night. Kith comes from the Old English cyðð, which means “kinfolk, neighbors,” and also “home, knowledge, and acquaintance.”