Nash Tringham is the father of Russell and Fletcher Tringham. He spent most of his life attempting to create a Red Stone through the use of the poisonous Red Water. His journey to uncover this alchemic amplifier did not, at first, interrupt his getting married and fathering his two sons, but at some point, he abandoned his family, either to immerse himself in his research, or to keep them safe from any repercussions that his career might land on them. He spent some time in Central, working in the mysterious complex known as Lab 5, but grew disillusioned with how the work there was progressing, and so left. Traveling from his hometown to the gold mining town of Xenotime, Nash joined up with the wealthy landowner Mugear in order to use the Red Stones in a way that would revitalize the failing city. He developed a method that would crystallize the Red Water much more quickly and effectively than usual, but when Mugear suggested another method to shortcut the effects, he refused to continue his research. Mugear wanted Nash to inject the Red Water directly into the unborn fetuses of pregnant women, so that the process of pregnancy would refine the mineral more efficiently, even though it might have a catastrophic effect on both the mothers and their children. Ultimately, this led to his assassination by Mugear.
When Fletcher first talks about his father with Alphonse, Alphonse suggests that the Tringham brothers have a very similar relationship with their father that he and Edward have with Hohenheim. Both have a father who appeared to care more about his alchemy than his family, and both men abandoned a wife and two sons with no obvious clues to their location. Also, both sets of brothers have innate alchemic ability, and choose to follow their father's goal. But while Russell worships his father's memory and wishes to bring his father's dream to fruition, Edward loathes Hohenheim and only wants to acquire the Philosopher's Stone so he can restore Alphonse to his human body.