Our Only May Amelia, a Newberry Honor Book by Jennifer L. Holm, has been suggested by Rebecca (when I asked for a suggestion two months ago, she gave me two books, and this is the second! Thanks, Rebecca!)
Here's a synopsis:
May Amelia is the only girl in the Jackson family and the only girl ever born along the Nasel River. Her family, including seven brothers, refers to her as the 'Miracle.' Sometimes it is great being referred to as the miracle, other times it is plain maddening. May Amelia thinks the real 'miracle' would be if the baby her mother is expecting turns out to be a girl. Will May Amelia be the only miracle? Or will the new baby be the sister she is wishing for?