Fletcher was Russell's younger brother, and the two of them specialized in plant-based alchemy. Unlike his older brother, Fletcher felt genuinely uncomfortable with their scheme to impersonate the Elric Brothers—he was also unsettled by what the Red Water did to people. When things escalated and Russell and Edward started fighting, Fletcher found himself getting along with Alphonse instead. Eventually, Fletcher's growing friendship with Al helped convince Russell to back off and stop the confrontation.
The brothers showed up again in the episodes "Goodbye" and "The Other Side Of the Gate," where they nearly faced execution for the whole Elric impersonation thing. Before that could happen, though, they tipped Ed off about the Underground City, which proved to be pretty significant to the story.
Note: There's some inconsistency in how the family name gets romanized across different releases. Sony's Aniplex DVDs use "Tringum," while their website uses "Tlingum," and FUNimation went with "Tringham."
Content compiled by AnimeList.moe from publicly available sources.
