We show the results of an extensive research on scenario evolution. We investigated twelve case studies spanning over 200 scenarios that contained over 800 episodes. The research aimed at capturing data on scenario evolution in order to confirm previous results and to elicitate the requirements for a scenario evolution support environment. Our findings are organised in a three tier framework, that deals with scenario evolution in the process, product and instance levels. We concentrate on the product and instance levels showing scenario relationships. Scenarios do not exist in a vacuum, they are connected to other scenarios in an intricate and complex network of relationships. We provide a taxonomy for classification and heuristics for the identification of scenario relationships.