Is he an ancestor of Ging and Gon? What is probably his story aside from being the author of the Book which talked about the Dark Continent?
Don Freecss is a character mentioned to have written a guide to the dark continent in two parts: East and West. The association has had a copy of East. West has not been seen. Ging claimed that is because Don is still writing West, and thus is still alive. East was written 300 years ago.
If Ging is correct, then these are valid assumptions:
- Don must be over 300 years old making him the oldest known character.
- The Dark Continent is notoriously dangerous so Don must be strong or well protected to reside there.
- Freecss is the last name of Ging and Gon so Don is likely related to them through Ging's father.
- As Nen slows aging and is the major source of combat power in the series, Don is likely a very power Nen user.
- As the Dark Continent is noted for having new/strange fauna and flora including powerful medicial plants, it is possible that his environment could greatly impact who the character is and provide a cause for his long lifespan.
That is all we know and can safely infer from the manga. There are fan theories surrounding him but at this point we don't know anything else.
I guess Don Freecs (grandfather of Gon) is someone who possessed Gon while he is in his fight against Pitou. Remember Gon was innocent and calm, and yet he become stubborn and fast temper. Maybe the author expresss the similar version of his another series like the Yu Yu Hakushou, when Yusuke being possessed by his father who were the most powerful person in the series in his prime.
Another hint that I can contribute is the gap between Gon and Don. Don somehow mention that he was 300 years (impossible) of age, close enough to like of the father of Yusuke in his another series. There is also other part of the world (Dark Continent) similar to his other series.
Don maybe the strongest character in HxH, who knows, he lives in a secret side of the world.
My guess is that Don Freecss is the great grandfather of Gon or later since over 300 years, many generations could've passed.
Now the question is, who is Don Freecss?
Don Freecss is a novel writer. I don't think he is involved in Gon's transformation. Why? If he was involved in it, then the transformation could have been a power passed over generations and generations and the Freecs family could've been the most powerful nen users.
Don Freecss was a nen user, but we can't confirm if all parts of this anime are related to Yu Yu Hakusho. That would be a crime. Don Freecss carries the characteristics of Ging Freecss, if you compare them. For example, Don travels a lot to discover new things like Ging does.
Don Freecss is probably an Enhancer. Why? The Zoldyck family has similarities in Nen. They are usually Transmuters or Manipulators. The only (rare) Enhancer in the family is the great great grandfather of Killua. Ging would be an Enhancer or Transmuter. I took the information by personality by Hisoka; I have not read it well yet, but Ging posseses the characteristics of an Enhancer and Transmuter.
Don Freecss's appearance is not yet revealed but my guess is that he looks slightly like Ging.
I agree with the theory that he may still be alive somewhere farther than the Dark Continent.
I believe he is immortal since Freecsses are amazing.