All that Eomer ever wanted was a brother, he wanted a brother like Theodred. He wanted there to be someone that he could play with and who he could race with when they were allowed to ride on their own. He wanted a brother who would be a soldier with him. So when he first heard his mother introduce his new sibling, he was shattered.
"Eomer, this is your sister - Eowyn" she said holding out the babe covered in pale fabrics to show him, and hiding a scowl ( for he was sure that if he showed it he would be in trouble with his father ) he looked obediently down at the babe, and saw the closed eyes of the girl and he thought her ordinary and ugly, and was about to state this when suddenly the babe opened her eyes and clutched his fingers in her tiny grip and she smiled and giggled.
And looking into her small, blue eyes he saw an inner joy - a joy to see him. The babe was happy to see him!. And so seeing that the baby wanted him to play with her - he did so. He never noticed the pointed, and happy, looks that his parents shared behind his back - all he cared about was that there in his mothers arms was his little sister, and he would do whatever he could to keep her smiling.