Lujon

Lujon is a character exclusive to the 2003 anime series. He is first introduced as a struggling young doctor in his small town studying medicinal alchemy in the hopes to cure a local plague called the "Fossil Disease" and also has a connection with Lust. At one point he was discovered by Lust, who, affected by memories of her original human counterpart with her lover and Lust's own creator thanks to Lujon's physical likeness  to the man, taught him more advanced forms of alchemy and gave him a fake Philosopher's Stone to help him cure his townspeople.

He'd been engaged to a woman named Lydia, and used the Stone that Lust gave him to heal Lydia from Fossil's Disease, the first successful cure. But as Lust helped him learn more about alchemy, he fell in love with the Homunculus, which Lydia started to realize as she watched the two working together. Lydia was set to marry Lujon, but on their wedding day, he left Lydia at the altar and confessed his love to Lust. Lydia rushed off after him and saw him embracing Lust, then stormed off angry and heartbroken. Lust, knowing she couldn't stay with Lujon as she had other plans and no real affection for him, told him to follow Lydia.

Sometime after the Homunculus left his side, however, the stone's power slowly began to fade and the fossil disease returned, causing him to flee in search of a new Stone. After some time, he finds Lust again as he'd secretly hoped, and she is quick to replace his old Red Stone for her own gains. When they finally return to town, he confesses his love for her once again; however, she's only brought back a little of her memories of her birth as a homoculi. He's shocked when she coldly kills him. Before dying, she states that he was her mistake (as she and Envy had been hoping for him to become astute and desperate enough to attempt to create a real Philosopher's Stone) and nothing more. His stone breaks and his body becomes fossilized from the disease that then kills everyone instantly in town. Lydia, returning to town with the Elric brothers and Winry Rockbell, finds him lying dead on the ground and embraces his corpse. Seconds later, Ed, Al and Winry find the couple, both dead and their bodies wracked with Fossil's Disease.

Trivia

 * Lujon's behavior reminds Lust of Scar's brother, who is both the Alchemist who made her and the lover of the person she was meant to replace. Ironically, Lujon's seiyū, Takehito Koyasu, went on to voice Scar's brother in the 2009 anime, where he is a much different character.
 * At one point after Lujon has used the Stone that Lust first gave him to cure Lydia, Lust meets with Envy, who had disguised himself as an old wagon driver.  The pair talk about their plan, and Envy states that "Fossil Disease" was generated by the homunculi as part of the hope of fostering the kind of desperation that might lead a talented alchemist to desire the true Philosopher's Stone.
 * A character in the Fullmetal Alchemist video game, Sonata of Memories, shares a physical resemblance to Lujon.