Human beings are unusual in the animal kingdom because of their capacity to self-reflect and to acquire self-knowledge. This means that humans often have the intention to look for their own dreams or ways of living that better fit with their interests and lifestyles.
One way in which humans look for this freedom and change is by choosing their partners. By choosing specific partners, human beings are able to create the family that they prefer and that they feel most comfortable with. Human beings also seek this change by choosing whether to have children or not, or whether to move out of their parents' home once they become self-sufficient.