I think that thw word kin comes from the exrpression next of kin = relative
word sib from sibling =brothers or sisters
So according to the meaning you should decide which one is what.
Actually it's not sib that is derived from sibling. It's the other way around. I know sib can mean sibling simply (at least that's what the dictionary says). And I'm not asking about this meaning.
My question is if these two words can mean exactly the same thing in this sentence. You didn't answer this question if understand what you meant. You just said they can mean different things. Is that right?