This paper presents a knowledge-based multi-agent framework (KGMAF) for automated requirements development. It is designed to address the problem that existing software engineering (SE) automation systems focus on code development and overlook the complexity of requirements work. KGMAF consists of six specialized agents and artifact pools to improve efficiency and accuracy. We describe the conceptual design of each agent's functions, behaviors, knowledge, and artifact pool. We demonstrate the potential of KGMAF in a real-world scenario through a case study and suggest several research opportunities for automated requirements development using multi-agent systems. We argue that KGMAF will play a significant role in shaping the future of automated requirements development in the LLM era.