Disclaimer: The usual disclaimer applies; I don't own them, I promise not to break them and I might give them back when I'm done.
When he was very young he had a nanny who would soothe him to sleep with gentle songs telling of blackbirds and bluebells, of brave knights and beautiful maidens. He would fall asleep dreaming of running through the woodland, of riding out beside his father to rescue a fair damsel in distress.
When he was seven years old he began training to become a knight and his nanny was sent away. Sleep didn't come easily and when it did his dreams were filled with armour and the proper way to serve venison and the best place to hide from the Master of Arms when he was in a foul temper.
When he was sixteen years old and had fought his first campaign he didn't sleep for three days. He'd close his eyes and see nothing but the flash of a sword and too much blood. He drank his wine unwatered and eventually his sleep was dreamless.
When he was twenty years old a boy saved his life and changed everything. He learned to sleep soundly, dreaming of always and forever, of hope and of destiny, lulled by constant chatter and a needle and thread pulled through a torn tunic.
When he was King there was a warm weight and steady breathing in the bed beside him. He would close his eyes and see his kingdom and his people, ravaged by too many years of poor harvest and of war. A hand through his hair would chase them away and a hand on his heart would send him into a deep sleep, never alone and always protected.