ABSTRACT
This chapter looks at the intense necessity to understand that twins are individuals in their own right, with a particular and special bond between them. Twins will experience the same phase of development simultaneously. They are in close physical and emotional proximity with another child born to the same mother, throughout their development. For other siblings, the differing sequences in birth and development and the differences in status that develop within the family, enable each child to find an individual path of development within the family context. Thus twins are siblings of a particular kind. For all infants, developmental figures exist in two dimensions: the primary relationship with mother (and father) is the vertical dimension, while siblings offer a horizontal dimension and play a significant role in helping the individual to negotiate and manage peer social relationships. A great deal of research has been carried out based on the assumption that MZ twins are genetically identical.
