This chapter provides an overview of the project. The project began with four initial insights that were used to guide the development of this work: 1) the existence of twin double primary attachments and double identities; 2) the lifelong struggles twins experience trying to create individual identity; 3) the importance of differentiation between the twin- and non-twin-worlds; and 4) the challenges twins face due to the deep psychological comfort that the twin-identity provides. The conclusion offers a summary of findings grouped into four primary categories: 1) the impact of the singleton-world on twin experience and self-understanding; 2) the consequences of early childhood experiences throughout the life span; 3) the reality of twin struggles in adulthood; 4) reasons for hope.