The families of the not too far-off past were related along 4 axes. These axes were not equally exclusive. Some overlapped, every one of them boosted each various other.
People got wed for various reasons:
1. As a result of social pressure as well as social norms (the Social Dyad).
2. To develop a more efficient or synergetic financial unit (the Economic Dyad).
3. In quest of psychosexual satisfaction (the Psychosexual Dyad).