Im reading a comic and this is the heading of the chapter. I looked up the english chapter and the translation was "Those who know power and solitude. Know nothing of each other". I'm wondering how they got the second sentence Know nothing of each other, I can't really deduce that based off the second sentence
それは変わることは無く means "That never changes", where それ refers to their strength and solitude. Just in case, this 無く is in the continuative form for this effect (see #3), and meaning-wise it's the same as simple 無い. So the second sentence does not mean "knowing nothing of each other". It's probably a simple mistake, but it may be a valid free translation based on the broader context, as @chocolate suspects.
If 強さを、孤独を、知る者たち = Those who know power and solitude.
And それは、変わることは無く= That will never change
Then, they will remain in solitude, which means they will not know each other.
Which is then reworded into "Know nothing of each other"
In a professional translation of literature, the translator will first understand the content and then write the story in their own natural language. That means that there will be places where you can't identify a 1 to 1 relationship in the translation between words or even sentences, especially in the case of English and Japanese. If the overall translation is good, as the OP has suggested in a comment, I find it very hard to believe this is a translation mistake. It seems much more likely that the significance of "solitude" is being emphasized for whatever events happen in the rest of the story.