Who are the flat characters in metamorphosis?

In Franz Kafka's "The Metamorphosis," flat characters include Grete Samsa, Gregor's sister, and Mr. Samsa, Gregor's father. Grete initially shows empathy towards Gregor but eventually grows resentful, embodying a static role that reflects societal expectations. Mr. Samsa primarily represents authority and familial pressure, exhibiting little development throughout the story. Both characters serve to highlight the themes of alienation and the impact of Gregor's transformation on family dynamics.