While Frain, 47, will be seen playing villain Theo Galvan, Lucas, 29, will play the role of his sister, Tigress.
Benjamin McKenzie, David Mazouz, Robin Lord Taylor, Camren Bicondova, Cory Michael Smith, Erin Richards, Morena Baccarin, Donal Logue and Sean Pertwee will all be back for the second season.
"Gotham" season two premieres on Monday, September 21 at 8 PM on Fox.