Leo Pierce -- Played by Steve Byers
Troy -- Played by Pedro Miguel Arce; Mary Kate -- Played by Mica Le John; The Asian Man -- Played by Nobby Suzuki
Mutant Type: Molecular (Multiple).
First Appearance: "Brother's Keeper."
Quote: Lexa: "Just do like we did as kids, okay? Just think of one good--one good thing."
Leo: "Lex. My one good thing is you."
Details: As a molecular multiple, Lexa Pierce's twin brother Leo could change his physical appearance and personality to become at least 8 different people, including a German police officer, a young black girl named Mary Kate, and an elderly Asian man. Once the twins developed their new mutant powers, their parents sent them to be raised in a military facility. Leo began losing control of his alters at 14, so Lexa joined the GSA in exchange for Leo's placement at a Genomex facility. Instead of receiving the treatments he needed, Leo was brutally tortured and told that they would harm Lexa as well if he told his sister what was happening. Trapped and alone, Leo was forced to develop his most dangerous alter Troy, who murdered two of the staff members in order to escape. Fearing that Lexa would send him back, or that a confrontation with Troy would end in her death, Leo avoided his sister for five years. Lexa tracked Leo with the help of The Dominion, trying to save him from capture by the ex-GSA security chief Charles Carter, who wanted to substitute Leo's heart for his own failing one. Before Lexa could reach him, however, Leo once again changed into Troy to protect himself from Carter's pursuit. Lexa tried to reason with Troy, but when Troy threatened Brennan Mulwray's life, Lexa wounded him with a laser. Troy then morphed back into Leo, who died in Lexa's arms.
Trivia: When Lexa first begins searching for her brother in "Taking of Crows," she tells the bar owner that his name is Luke. Then, when she's searching for his name among the past residents of St. Pastor's Hospital in "Shadows of Darkness," she types in LEO PIERCE. The camera pans to her face and then back to the computer screen...where the name has magically been changed to "LUKE PIERCE."