The universal phantasy of having a twin originates in our earliest relational experiences. This book is about twins and twinning processes. The existence of an actual twin, alive or dead, may be experienced as an embodiment of the phantasy of having a twin, with developmental consequences. Twinning processes in twins lead to the creation of an internal twin relationship that is enduring. The twin relationship may be at the narcissistic end of the spectrum leading to an enmeshed twinship, or it may be a more mature object relationship. All twin relationships will be manifest in the transference relationship with the analyst. The twin transference has been largely neglected in the psychoanalytic literature, to the detriment of our understanding of dynamic processes in twin patients. Case material is used to explore the nature of the twin transference relationship and the necessity of analysing the twin transference, as well as maternal and paternal transference relationships.