Long ago, there was a kingdom that was prosperous and peaceful. It was a curious place, for it had been ruled by the same philosophy-engineer-mathematician-astronomer-artist-musician-king for the past seven hundred years.
The king was not immortal in the sense that we think of it. However, he was immortal. You see, when his death nears he performs The Great Rite. He drinks a potent potion, the formula of which is known only to him, and then makes passionate love to his queen. The effects of the potion when combined with his climax kill his current body. However, the potion also guarantees the fertility of his seed and that it will produce a male child. Into this child he is reborn.
As the King knew, memory is stored within the cranium, as can be demonstrated by those unfortunates who have had damage to their brains. So, the newly reborn king does not have his old memories upon completion of the transmigration of his soul. Fortunately, he has trained his Queen to act as regent while training him to be King anew. When the Queen-mother passes, then the King seeks a new wife among the kingdom. All maidens are honored to be considered, for the queen is treated with great dignity, given how important she is to the kingdom.