https://gotham.fandom.com/wiki/Jerome_Valeska

Jerome Valeska was a deranged, mass murderer and anarchist. He was the more vengeful and chaotic twin brother of the obsessive and methodical anarchist mastermind, Jeremiah Valeska.

Born and raised in Haly's Circus, Jerome murdered his mother roughly at the age of eighteen, which led to his arrest and incarceration at Arkham Asylum. Following a breakout with other inmates orchestrated by Theo Galavan, he became the leader of The Maniax and wreaked chaos upon the city. This later led to his betrayal and murder at Galavan's hands, although his death brought about an underground movement devoted to him and his way of thinking.