This one's based on a prompt from Raina, but in order to not give away the ending, I wrote the prompt at the bottom of the story rather than here.
I also added a song which I of course do not own the rights to, called "Come Again" by anonymous, but first written down by John Dowland in 1597.
Takes place in AU where the Pevensies rule Narnia and Caspian rules Telmar.
Their life had been as perfect as a picture. But that was all it was, a picture. But as she returned to her husband in Telmar after a long trip to visit her father and the other stars for a few years, Lilliandil was sure that would change.
"Queen Lilliandil," Caspian greeted, with a formal bow. A familiar pang of jealous rose in her. If it had been his Gentle Queen who he had been greeting, he surely would not act with this unfamiliar formality.
"My King," she said. "I have wonderful news."
She gestured to the servants who brought out a small bundle.
"What is this?" Caspian asked curiously. The star's child smiled as she lifted the bundle and handed it to him. "A child? But… I haven't seen you in 2 years."
"Stars' pregnancy is different from human pregnancy," she said. "And the child is already almost a year old. But could anyone deny that this is your child?"
Sure enough, the child looked just like his father. "He most certain does look like me," Caspian wondered. "But even if he hadn't who am I to judge? Queen Susan of Narnia was here and – "
"Yes, I know," she said, an uncharacteristic nasty look upon her face. But then her face smoothed out, and she said, "But she died, and nothing will come between the three of us ever again."
Caspian had lived a good, full life. He was ready to die once his son had been returned to him by a visiting lady and gentleman from Narnia. But he was surprised to find himself in Aslan's country once he died.
"But I am a Telmarine," he wondered out loud.
He was surprised to hear a voice behind him answer, "There is one here waiting for you."
Caspian turned just seconds before the Lion began moving. He knew he must follow. But at one turn, he lost the Lion altogether. He was about to despair, but then he heard a beautiful voice singing.
"Come again, sweet love doth now invite. Thy graces that refrain. To do me due delight."
He climbed a wall to see a mane of hair spinning about as the sweet voice trippingly sang, "To see, to hear, to touch, to kiss, to die! With thee again in sweetest sympathy."
Caspian smiled at the beautiful love song. But then her voice, while still quite alluring, grew bitter. "All the night my sleeps are full of dreams. My eyes are full of streams. My heart takes no delight."
She began dancing again as she spat out, "I sit, I sigh, I weep, I faint, I die! In deadly pain and endless misery."
"Maiden! Why do you sing such sad songs whilst in Aslan's country?" he asked as he climbed down the wall. The maiden turned, and he gasped when he saw it was Susan.
"Queen Susan!" he exclaimed.
"King Caspian?" she gasped. For a moment her eyes seem to light up, but then they turned cold as night. "Leave me be."
"I… I couldn't help but hear your beautiful song. I do not mean to be presumptuous, but as far as I know of, I am the only man you have been with. I would like very much to know if that song was about me," he said.
Her eyes narrowed dangerously. "The first verse was to the memory of you as you once were. Or at least who I thought you were. Before you and your wife betrayed me."
"You already knew I had a wife when I slept with you!" he protested. "I wish I hadn't had to end things, but I had a responsibility to stay with her. I only wish I had known how much that hurt you."
"You think I weep because you left me? Nay, you flatter yourself. I did not weep for one second for a villain like you. I weep for my son you and your wife stole from me," she hissed.
"Wh-What?" Caspian said, shocked.
"My Rilian, my precious baby. My sweet, sweet baby. One moment I am sleeping with my newborn child in my arm, the next I am dead. And from here I could see you and your wife passing my child off as yours. How dare you?" she accused.
"What?" was all he could manage to say for quite some time. He finally managed to regain his voice and said, "I… I swear to you on my father's grave I knew naught of this."
She leaned back and blinked in surprise. Slowly, hesitantly, she asked, "No one can lie in Aslan's country. You… you are telling the truth?"
"I swear I am," he said. "How… how can I make it .. Never mind. I know there's nothing I could do to ever even come close to making up the hurt you feel."
"I suppose you are not to blame," she said in a small voice. Caspian took her in his arms as she began to cry. He rubbed her shoulders and the small of her back, whispering words of comfort in her ear.
Susan finally pulled away from him, her eyes still glistening with tears. "I've hated you for so long that it seems so strange to hate you no more."
"I just can't believe all those years we lost that could have been spent together. But now we have an eternity together here in Aslan's country. I consider myself blessed beyond compare, my sweet love," he whispered.
Susan smiled and fell into his embrace once more.
So the prompt was: Could you write one about Rilian being Susan's son but Caspian not knowing while Liliandil pretend he is hers since Susan dies.
And in case you didn't know, the reference to dying in the first verse of the song is from when dying used to mean sleeping together. (I'm not sure why anyone would compare the two, but okay…). Second time I'm pretty sure they meant dying the way we define it today.
By the way, I've been getting some really great prompts lately from my reviewers! Sorry it might take awhile to get to all of your prompts. My goal right now is to attempt one a week. There's also a few prompts for this story which I ended up or will end up incorporating in full story with Suspian in it called What the Horn Wrought, so if after awhile you still don't see a oneshot with your prompt here, it may be there!