Link's relationship with Zelda has been developing as the story flows. In lore, Link, Zelda, and Ganon (the evil) represent three pieces Triforce, corresponding to Courage, Wisdom, and Power, respectively. The three are destined connected in an endless cycle.
People speculate that Link and Zelda are in a possible romantic relationship. Although not told by the story, there is evidence in and out of the games that this relationship is true. The game producer, Eiji Aonuma, once said otherwise that it was not their intention to create a romantic relationship between the two, but to the most important person for each other.