A friend of Edward's from Resembool when they were younger, Pitt Renbak was older than Ed by a couple months and they always would compete against each other in various things. For one thing, they always competed on how tall they all were, maturity, skill, and etc. When Ed and Al left to search for their bodies, Pitt soon left not long after and went to a remote town to learn herbal remedies. The friends reunite when Ed gets a high fever from traveling so long and Al brings him to the town to rest. As Ed gets better, the friends recall times back in Resembool including when Ed wet his sheets and hung them outside while it was raining to hide the evidence.
The plan would have worked if Winry hadn't been walking by just then though. Another time was when Pitt and Ed "accidentally" forgot to sweep the floor before recess at school. The girls yelled at them so the boys plotted revenge by scooping heaps of pillbugs and throwing them head on into the classrom at the girls. The plan was a success until Winry picked up every pillbug and stuffed them down the boy's shirts while they were basking in their new found glory.
Ed feels upset during his time there, as he believes that Pitt is regarded as successful and grown-up, training to be a doctor and taking responsibility, whereas he has gotten ill because he didn't listen to Al and slow down sometimes. But Ed discovers that Pitt feels the village, and one family in particular, don't trust him because of a mistake he made not long after he started his training. Pitt also believes that Ed has much more recognition and respect as a State Alchemist.
Pitt was shown to be jealous of Edward not only because Ed was important and influential, but because he was in love with Winry. Pitt returned to Resembool briefly after he made the mistake with his herbs, only to find that Winry was learning how to make stew, which is Ed and Al's favorite meal. He was sad that Winry was only thinking of Edward, who never gave a thought about her, while he cared about her but was overlooked.
Ed and Pitt continually bicker about which of them is taller, challenging Al to measure them, although Al refuses to do so. At the end of the story, Pitt throws a bottle of paint remover at Al to get rid of the measurements that he took of himself and Ed while they weren't looking. He claims that he beat Ed by a half inch.
The only pictures of Pitt in the light novel are from his childhood in Resembool. He is a curly haired boy of similar height to Ed. In the novel, Ed remarks on the fact that Pitt is wearing glasses, but Pitt reveals near the end that he was only wearing them in order to appear older. When Ed tries on Pitt's glasses and asks what Pitt and Al think, both boys tease him that it doesn't help Ed look any older.
Although Pitt feels disappointed that Winry only seems to think of Ed and Al, during the novel, Ed does think of Winry sadly more than once, and admits to himself that one of the reasons he doesn't want to even make contact with Resembool is because he's afraid that if he returns home, the warmth and affection he knows will be there would dramatically increase his reluctance to resume his search for the Philosopher's Stone.