Middleware platforms must satisfy an increasingly broad and variable set of requirements arising from the needs of both applications and underlying systems deployed in dynamically changing environments such as environment monitoring and disaster management. To meet these requirements, middleware platforms must offer a high degree of configurability at deployment time and runtime. At Lancaster we use reflection, components and component frameworks, and middleware families as the basis of our approach to develop dynamically configurable middleware platforms. In our approach, components and component frameworks provide structure, and reflection provides support for dynamic configuration and extensibility for run-time evolution and adaptation. This approach however has contributed to make the development and operation of middleware platforms even more complex. Middleware developers deal with a large number of variability decisions when planning (re)configurations and adaptations. This paper examines how Model-Driven Engineering (MDE), Domain Specific Languages (DSLs) and System Family Engineering can be used to improve the development of middleware families, systematically generating middleware configurations from high level descriptions. We present Genie, a DSL-based prototype development-tool that supports the specification, validation and generation of artefacts for component-based reflective middleware. In particular, this paper describes how the Genie toolkit improves the development of the Gridkit middleware through the modelling and automated generation of middleware policies; that remove the complexity of handling large number of runtime adaptation policies.