kith and kin

I think I know what you are trying to say, but "nine degrees" is not a term we normally use when talking about "kith and kin" which is itself archaic. So my answer is that it is not instantly understandable.

Then would you suggest an expression?

What's the significance of "nine degrees"? Why not ten, or some other number?

For "kith and kin", nowadays we just say relatives, or blood relatives (although that excludes those related by marriage), or even just family, or extended family.
It depends on the wider context of what you want to say.

The above quote is an Emperor's remark, about his decision of the fate of the corrupt official and all his family members and those related to him by both blood and marriage. It was a very cruel practice in ancient China.

The so-called nine degrees (jiu zu) may not be a correct expression. There are two definitions:
First: it refers to the 4 generations before the ego and 4 after him, that is great great grandfather, great grandfather, grandfater, father, ego, son, grandson, great grandson, great great grandson.

Second: 4 generations on father's side (children of father's sisters, children of one's sisters, children of one's daughters, and the ego's parents, brothers and sisters, and children), 3 generations on mother's side (maternal grandfather and grandmother, and maternal uncles), and 2 generations on wife's side (father-in-law and mother-in-law).

Now that you have some idea of what it is meant here, do you have an expression to describe this concept of "jiu zu"? Or can we use "clan" in regard to the above context?

Within the context you've provided, the sentence seems fine, Fansy, except that the term kith in kith and kin doesn't really mean what you want. 'kith' means acquaintances.

And as to the fates of relatives in accordance with the Chinese concept known as jiu zu, they are still in the balance.