Abstract
A developmental guide to close relationships is presented. Parent-child, sibling, friend, and romantic relationships are described along dimensions that address permanence, power, and gender. These dimensions describe relationship differences in organisational principles that encompass internal representations, social understanding, and interpersonal experiences. The concept of domain specificity is borrowed from cognitive development to address the shifting developmental dynamics of close relationships. Distinct relationships are organised around distinct socialisation tasks, so each relationship requires its own organisational system. As a consequence, different principles guide different relationships, and these organisational principles change with development.