Belsio is a farmer that lives in Xenotime and an old friend of Nash Tringham. Similar to the other Xenotime characters he was first introduced in the first Fullmetal Alchemist Light Novel: The Land of Sand, and later adapted into the 2003 anime.
Despite Xenotime's suffering through poverty from the lack of wealth, Belsio was the only resident who was unconcerned about using the Philosopher's Stone to revive the town's wealth. Years ago when Nash came back from Central, after he mentioned about never wanting to go back, Belsio witnessed as the wealthiest landowner Mugear talked Nash into helping him. Once the newborn children became sick and started to die, including Elisa who was nearly a victim had it not been for Tim Marcoh's help, Belsio confronted Nash, and Nash realizing how guilty he was stated he was going to make things right before he was never seen again.
In the present, while dealing with problems from Elisa's father into letting her help him in the fields, Belsio offered his place to stay for the Elrics brothers after they were accused of being impostors thanks to Nash's sons Russell and Fletcher stealing their identities to continue their father's research. Not caring if the Elrics were telling the truth, Belsio watched ideally as the Elrics kept breaking into Mugear's mansion to discover the truth.
Eventually, after learning from the Elrics about what the impostors said, Belsio realized they were actually Nash's sons and told the Elrics the whole story, essentially assisting Ed in uncovering the truth, and enabling Ed to plan out what to do. Later after Mugear's death, Belsio agrees to let the Tringham brothers assist in helping out on his farm, to have their plant-based alchemy work towards raising good crops in dealing with Xenotime's poverty.
- While Elisa is identified as Belsio's niece, it is unknown about Belsio's relation with her father, whether if they are brothers or brothers-in-law.