This thesis explores how synergies between system family engineering, model driven engineering, and generative software development help to produce new development paradigms to support design, programming, testing, deployment, and execution of reflective middleware families and their applications. The thesis proposes Genie, an approach that guides the development and operation of reflective middleware platforms and their applications. Genie oers management of dynamic variability during development and allows the systematic generation of middleware related artefacts from high level descriptions (models). To this end, two kinds of dynamic variability are identied, namely structural variability and environment and context variability. As a validation of the approach, a prototype called the Genie tool has been developed. The Genie tool supports the speci cation, validation and generation of artefacts for component-based reflective middleware using domain specic modelling languages (DSMLs). The approach has also been used to support the development and operation of Gridkit, one of the dynamically congurable middleware families that have been developed at Lancaster University.