A Song of Blood and Sapphire - Aemond Targaryen

Rhaenerys Velaryon and Aemond Targaryen were born within hours of each other, one with the moonrise and the other with sunset. To "mend the bonds" between their two families, the King decreed their shared name-day be a week long celebration. While the festivities never brought their mother's any closer, their two children became thick as thieves. Some went as far as to suggest they were twins born of different flames.

But a line had been drawn between them the night Aemond lost his eye, and her little brother had been the one to carve it.

When Aemond and Rhaenerys are reunited for their twentieth name-day, the princess finds herself considering just how much she's willing to bleed to prevent the coming war. She is uncertain whether reigniting that old flame will change her family's fate, or seal it.

"If you've returned home expecting to find that sniveling doe-eyed boy, who hid behind his mother's skirts, then you are a fool." Aemond released her wrist, standing to his full height. "I gutted him."
"That's a shame," Rhaenerys whispered, and despite towering a full head above her, Aemond felt puny under her gaze. "There was a time when I loved that boy with all my heart."