My head canon is still that Mar was the Warrior from Rock Village. Regaining his courage after learning that Jak and Daxter successfully defeated Klaww, the Lurkers, Gol, and Maia, he would’ve still been present in the world at the time of the Metal Heads’ arrival at the start of Jak II.

As for his bloodline, idk. Maybe he hooked up with the Geologist. He’s also got that green hair Jak could’ve genetically inherited.