Every human relationship begins with a coincidence. Even the most fundamental relationship - that of parent and child - begins entirely with a coincidence. The child is produced by whatever serendipity brought its parents together, and the fact that the child was born to its particular parents instead of to another couple is pure happenstance. Thus, children have no choice over the relationship that is most important to their existence. By contrast, friends and lovers choose each other, but even these choices are reactions to whatever random coincidence made the resulting relationship possible.