What is the relationship between Louis XIV and Louis XV?

Great-grandfather and great-grandson. As for the reason, Louis XIV married a close relative of his wife, and only one child survived, that is, Prince Louis. Prince Louis has three sons, namely, the grandson of King Louis, King Philip V of Spain and Charles. The king of Spain is the heir, and France and the Spanish royal family are related by blood, so Philip V succeeded to the Spanish throne. The Holy Roman Empire was dissatisfied and started a war. France won, but the treaty stipulated that Philip V gave up the right to inherit the French throne (otherwise France and Spain would be invincible if they merged). Then, a few years later, Prince Louis, Charles, the great-grandson of King Louis, and the eldest son of the great-grandson of King Louis all died, and Charles had no heir. Therefore, Louis XIV has only one great-grandson Louis XV as heir. ...