When the Telmarines invaded Narnia in Narnian Year 1998, almost one thousand years after the end of the Golden Age and the disappearance of the High King Peter and his siblings, the Mayhew Witch Clan placed a curse upon King Caspian I, then known as Caspian the Conqueror. The Mayhew Witches cursed Caspian I and all his male descendants with early deaths of sons, and their wives with difficulty bearing children and still-births.
The Telmarine Kings were, of course, unaware of this curse, since the Old Narnians had been driven into hiding after the Telmarine Conquest. But all the kings in a direct line of Caspian I were either only children or the only surviving child of their parents. All took the name of Caspian when they assumed the throne, no matter which name they'd been born with.
Despite, or perhaps because of the curse, the descent line of the Caspian kings was fairly peaceful and unbroken until King Caspian VIII and his wife, Queen Violet, had two sons who both survived childhood: Caspian IX and Miraz.
Caspian IX married Elisabeta, daughter of Duke Manillo of Glassmoor. They had one son, Caspian X. Caspian IX was murdered by his brother Miraz, when Prince Caspian was two years old. Queen Elisabeta fell ill and died two years later (and rumors of poisoning spread through the court). Miraz, Prince and Lord Regent of Narnia, began styling himself as "King" with Prince Caspian as his heir, not long after after the Queen's death.
Miraz and his wife, Prunaprismia, had one son, Abelian. After the death of usurper Miraz in the Second Battle of Beruna during the Narnia Revolution (or the War of Deliverance), King Caspian X pardoned the Lady Prunaprismia, and she and Prince Abelian were allowed to stay in Narnia, in the home of her father, Lord Scythley.
Caspian X married Alecto, the daughter of the Star Ramandu, whom he met while voyaging on the Dawn Treader to the End of the World. The curse on the Caspian line did not abate, despite Caspian X uniting Telmarine Narnia and Old Narnia as one country, with the aid and blessing of both the High King Peter and of Aslan Himself. Caspian X and Queen Alecto had four stillborn children before their son Rilian was born.
When Prince Rilian was 12 years old, his mother Queen Alecto was killed on a court outing by a poisonous serpent. Soon after, Prince Rilian disappeared. For several years, King Caspian X searched everywhere for his son, but after the deaths of many knights and brave Narnians, he forbade any further searches, and turned to Aslan for help and guidance in finding the missing prince.
After several years, Prince Rilian was returned to Narnia, found by Puddleglum the Marshwiggle and two children sent by Aslan to aid in the search. King Caspian X died very soon after the return of his only son, and Rilian ascended the throne, the first of the House of Caspian to not take the name Caspian as King.
Rilian's reign was troubled in the beginning, as many Narnians were skeptical that the long-missing Rilian was who he claimed to be. There was a movement to put Miraz's grandson, Favian, son of Abelian, on the throne, but King Rilian's lineage as both a son of stars and true heir to the Narnian throne was proven, and he reigned with no further challenges until his natural death at age 60.
King Rilian and his wife, Queen Maranel, had two children who survived into adulthood, both sons, Ghosian and Levian. Ghosian, the eldest son, succeeded Rilian as King of Narnia, but was killed in a riding accident less than a year into his reign. Ghosian was unmarried and childless, and his brother Levian took the throne.
King Levian and his wife, Queen Ivy, had three children: two daughters, Clio and Cordelia, and a son, Cibrian. All three children were born healthy and survived their childhood, the first in several generations of Caspians to do so.
It was during the reign of King Levian that the rumors of the curse on the House of Caspian surfaced once again, and Levian sought out Niamh Mayhew, who was, at the time, head of the Mayhew Witch Clan, to discuss the truth of the curse and lifting it. Niamh Mayhew claimed that the origins of the curse had been lost over the years, and that without knowing those, it was impossible to lift it completely. However, she suggested that uniting the Mayhew Clan with the House of Caspian could abate the curse, as the curse would not work against the Mayhews themselves.
King Levian agreed to unite the families, but his oldest child and heir was a daughter, Princess Clio, and Niamh Mayhew insisted that the curse would only abate if one of her daughters married Levian's son. Princess Clio abdicated her right to the Narnian throne, and sailed to the East, seeking the island of her ancestor, the Star Ramandu, and was never heard from again. Prince Cibrian married Kelleen Mayhew, and ascended the throne after the death of King Levian.
—- Histories of the House of Caspian: The Age of United Narnia, by Myrcella Abelian, Est. Scholar, Beruna Acadmic Press
"It isn't fair!"
The loud protest was not unexpected, nor was it incorrect, Cordelia thought, as she watched Clio pace angrily around her bedchamber, her blonde hair standing in frazzled ringlets, evidence that Clio had been running her hands through it over and over, as was her habit when she was frustrated.
"You're right," she agreed, keeping her own voice low. It wouldn't do for Papa and Mama to hear both of them shouting. And it wouldn't help anything anyway. But Clio's loud protests continued.
"I'm to be the Queen, not Cibrian! All my life, I've prepared — trained! Who has sat by Papa's side in every council meeting for the past five years? Not Cibrian! Who traveled to Terebinthia to settle the country after the pirate attacks? Not Cibrian! Who did Papa and Mama betroth to that insipid Duke Merton from Galma? Not Cibrian!"
At that last, Clio ceased her pacing and glanced at Cordelia, who was sitting crosslegged in the center of her sister's bed. "Do you suppose I still have to marry him if I'm not going to be Queen?"
Cordelia was not surprised at the question, since this betrothal had long been the bane of her sister's life. Her answer came after a moment of thought. "Well, I suppose that Papa and Mama would like you to, to keep the peace with Galma. Betrothal to a princess is not as prestigious as to a Queen, but I imagine he'd still want you for a wife." She paused. "Still, after stripping you of your birthright, I don't think they'd force you to do this."
Clio nodded at that, a wry smile crossing her face. "They had better not think to try."
It was the first time Cordelia had seen her sister smile in three days, since the meeting with the Mayhew Witch Clan. Niamh Mayhew had made the terms very clear: Cibrian would marry her daughter Kelleen and ascend the throne, and with the children born of their union, the curse would abate. But that meant that Clio had to abdicate her her right to the throne of Narnia, because according to Niamh only a daughter could marry to lift the curse, not one of her sons.
(Privately, Cordelia wasn't sure she believed in the curse or not — it seemed to her more like coincidence and a run of bad luck, but her father and all the other believed it, and her opinion on the matter wasn't sought.)
Papa had agreed to the terms, as was his right as King of Narnia. Cibrian, the new heir apparent and newly betrothed, had agreed as well, although a bit reluctantly. But Clio, as Crown Princess and heir to the throne, most very definitely had not.
Papa had insisted that Clio forfeit her right to the throne, rather than he have to formally disinherit her. He had said it would cause bad feelings within Narnia if he did so (although Cordelia rather thought that Cibrian marrying one of the Mayhew Witches and taking the throne was bound to cause some bad feelings, no matter the manner in which it was achieved). Clio had refused, stating she had made no agreement with the Mayhew Clan, and if Papa wanted Cibrian over her, he would have to be the one to make the decision.
The halls of Cair Paravel had rung with the arguments as she and Papa had shouted back and forth, as Mama had joined in to try to soothe and make peace, and as Cibrian foolishly added his own opinions and received a stern smack from both Papa and Clio. Cordelia had wisely kept her own mouth shout. The discussion — Mama's term — or screaming row — Cordelia's — had gone on for days, until Papa had finally banished Clio to her chambers, telling her to stay there until she "came to her senses."
Cordelia had been the only one to brave Clio's anger and visit her chambers. Her sister was angry, and rightfully so, but even as stubborn as Clio was, Cordelia couldn't imagine she wouldn't give in eventually. Because Clio had been raised to be queen, and to think of Narnia first. She would give in, rather than risk tearing the country apart.
"You can refuse him," she said now to her sister, watching as her smile grew wider. "You realize you can refuse many things now, don't you?"
Clio's smile faded. "I can refuse if I agree, you mean."
"Well, yes," Cordelia agreed. "But don't you think you should? Rather than force Papa's hand, I mean. If he has to disinherit you, he'll be most displeased. He might even make you still marry Duke Merton. But if you step aside for Cibrian, on your own, you can make your own terms."
Clio turned and stared at Cordelia, her eyes going wide. "My own terms?"
"Of course! You're looking at this the wrong way, Clio. You're thinking of it as a battle you've already lost, and you're the defeated party with nothing to gain. But you should negotiate the terms of this agreement with Papa! If you agree to step aside for Cibrian, well then, you should have compensation! First, you shouldn't have to marry Duke Merton. Second… well, I don't know. Think of what you want, sister!"
"What I want?" Clio sounded almost puzzled by that. "I … I've never been able to think of that. I've only thought of how I must serve Narnia."
"And now you no longer need to! Didn't you say to Cibrian and me that we were lucky? Since we could always be prince and princess, and never king or queen? We never had the responsibilities that you always have had. Now you can be free of those! You can make your own life, your own choices. That should be part of your terms."
"What I want…" Her sister repeated it again in a wondering tone. Then she turned from Cordelia and crossed the room, stopping in front of the balcony that overlooked the Eastern Ocean. She stood for a long moment, staring at the sea in silence, and Cordelia wondered what it was that her sister actually wanted.
The answer, when it came, was surprising. "I want a ship."
"A ship? For yourself?"
"I want to travel east," Clio said. "Like Great-Grandfather Caspian did on the Dawn Treader. I want to find the Island of the Star. I want to sail to the End of the World."
"Do you believe all that, Clio? Still?" When they were children, it was Clio's favorite story and Cordelia and Cibrian had often acted as crew to Clio's Seafarer when they played make-believe.
Her sister turned away from the balcony, and though she was calmer, there was still a light blazing in her dark blue eyes. "Yes, still. And it's what I want. If I can't be Queen, if they mean to take that life from me, I'll have an adventure." A smile slowly spread across her face, a true smile this time. "Tell Papa and Mama, Cordelia, that I will agree to step aside for Cibrian, but there are terms that must be negotiated."
Cordelia stood from the bed, smoothing the wrinkles in her dress. If she was to meet with Papa and Mama on Clio's behalf, she should look presentable. "I will. And when they are ready to negotiate, I will send for you." She paused at the bedchamber door, looking back at her sister. "They won't like this, Clio."
"No." Clio shook her head. "No more than I like what they're asking of me. But they will agree, just as I have. To keep the peace."
"Very well. I will tell them." Cordelia opened the door, but a word from her sister stopped her.
"Make sure you tell them you're going with me."
"Me?" Cordelia was shocked. "You want me to come along?" It wasn't an adventure she had ever dreamed of, but now that she thought of it, the idea of a journey far from home held a great appeal. "They won't like that even more." But she was smiling as she said it.
"Too bad. We're princesses, not queens. We get to have fun. Together."
 Unlike the witches who came from the North (Jadis the White Witch, and The Green Witch), there were — and still remain to this day — native Narnians who practiced a different sort of magic, elemental magic. The Mayhew Witch Clan's origins date back before the Golden Age and the 100 Year Winter. They claim descent from one of the daughters of King Frank and Queen Helen, and through their intermarriage with centaurs, their daughters are often gifted with second sight, and the ability to predict the future.
 There are conflicting sources on this, some of which claim that Rilian was 18 years old at the time of his mother's death. But the official palace documents, among them the journals of King Caspian X, place Rilian's age at 12 at the time of his mother's death and his disappearance.
 The children were said to be visitors from beyond the world, brought to Narnia by Aslan to accomplish this task. Rilian recorded the children's names as Jill and Eustace, and it is said that Eustace was kin to Peter the High King, and traveled with King Caspian on his voyage to the World's End. There is no actual evidence to support this claim, but it does align with the legend of the Kings and Queens of Old coming to Narnia from a different world, and returning to it at the end of the Golden Age.
 A dramatic incident in which several stars descended to earth on the eve of Caspian X's burial, witnessed by several hundred Narnians at Cair Paravel.
 There are many who believe this is untrue, and that Niamh Mayhew was simply manipulating King Levian to gain power for her family. However, Levian trusted her word, and there is no evidence that she was deceiving him.
 Her sister, the Princess Cordelia, joined Clio's journey into the east, and returned to Narnia claiming that Clio was able to journey not just to Ramandu's Island, but outside of the world entirely. See: Diaries of Princess Cordelia, and The Second Journey to the East, by Magnus Clearwater of Beaversdam University.