What is the science behind relationships?

Is there a theory of relationships? Any science at all of what a relationship is, what kinds there are and how to create them? It's as bad as science of leadership and business.

I propose this hierarchy as a start:

Physical: The gestures of the body, spoken sounds, etc.
Concepts: These are assembled into emotions, words, etc.
Statements: All the concepts are combined into a single statement.
Interactions: An exchange of statements, acknowledgements, etc into a type of interaction. They could be short, transactional or they could be conversations. There are many types of conversations: for example exchanging information or learning, decision making, establishing intimacy and trust or resolving conflict and reinstating respect.
Relationships: Over time a series of interactions evolves into a relationship. There are many types of relationships, but Aristotle's Rhetoric comes to mind here.