Originally Posted By: Faldage

Kith are people you know; kin are people you are related to.


Yes, but they're all people of importance in one's life, some more, some less, who have direct influence, and in many practical ways are not that different. I interpret time and tide to mean time and events, which are not strictly identical, but of no practical difference within the scope of the adage. To me those are shades of difference, close enough to be considered redundant.