Your kin is, of course, your family. Your kith is everybody you know. Indeed, kith originally meant knowledge. Those who are not your kith are unkith, and therefore uncouth, which originally meant unknown.
Uncouth comes, it seems, from cuð, which gave the Old English wīfcȳþþe, which meant woman-knowledge, which meant rumpy-pumpy. But now uncouth survives as a fossil word like gormless, feckless, ruthless and reckless, on which I have already blogged.
However, according to the dictionary, couth has survived in Scotland (although I don't see why anything would want to do that). In those cold, hyperborean, whisky-sodden glens couth's meaning has moved from known to familiar to snug and cosy.