Why does Dragon Quest V span three generations?

Dragon Quest V (1992) opens with a birth and then follows its hero for roughly thirty years. He travels as a small boy at his father Pankraz's side. Pankraz is killed protecting him, and the boy spends ten years enslaved, building a temple for the villains. He escapes, grows up, and reaches the decision the structure was built to hold: marriage, chosen by the player, to Bianca, the childhood friend who explored a haunted tower with him, or to Nera, a wealthy man's daughter whose hand is the prize of a trial. A third bride, Debora, was added in the DS remake, a choice Horii himself described as one nobody in their right mind would pick.

The generations are the plot's engine, not its frame. The hero's father spent his life searching for the Legendary Hero who could wear the Zenithian equipment and face the darkness. The hero takes up the same search, marries, and has twins. Turned to stone, he waits eight years as a statue while his children grow up without him, and when they finally free him, the search resolves the way the whole game has been pointing: the Legendary Hero is his son. Three generations are not three acts. They are the answer to the first act's question.

The structure carried firsts with it. V is credited as the first known video game to feature a playable pregnancy, and it introduced the series' monster recruitment, so the party itself spans species as the family spans years. Critics singled out the division of the story into life periods as something very few games have attempted, and Gamasutra's verdict on the coming of age theme stands as the summary: never has it been executed so magnificently. In Japan, where the game sold 1.3 million copies in a day and placed eleventh in Famitsu readers' all time poll, the three-generation span is simply what Dragon Quest V means.