Explorer

The Explorer, Jak's Uncle, lives in Sandover Village in retirement. When Jak and Daxter set out on their mission to the north the Explorer asked Jak for some Precursor Orbs for supplies. They gave him the Orbs and received a Power Cell in return. It was revealed by Naughty Dog that Jak's uncle was created before the thought of using time travel in the game and so, he wasn't tied into the series or Jak's family after the Precursor Legacy.

Pre precursor legacy
[Note: The following information may be mendacious]. The Explorer could possibly be the ancestor of the original Mar, due to the resemblance to Jak and the long span in the timeline (300 years). This would fit with the theory that Jak is the descendant of Mar. The usage of Jak's "uncle" could have been an agreement between Samos and The Explorer or the Precursors, upon the arrival to the past; that he would look after Jak as he grew up posing as family.

Precursor Legacy
The Explorer "or Uncle Yubith" is a villager, seeming to be an explorer. He lives in Sandover as a retired geologist. He asked Jak for precursor orbs for some suplies, in return he gave them a power cell.

Attire
He seems to be well dressed in villager's cloths, with an eye glass, with a cane, holding a Green Eco Seed.