Sister Mine

When Makeda and her twin sister Abby are born, they come into the world conjoined and sickly. The surgery to separate them weakens Abby so much that she will surely die-unless her parents make a bargain with the gods. For Makeda and Abby are not ordinary children, they are the offspring of Boysie, god of growing things, and his wife, a beautiful human woman. In exchange for Abby's life, Boysie agrees to live as a human, and his wife must spend her days as a monstrous sea creature.
Twenty years later...
Physically healthy but with no magical ability, Makeda has spent her whole life in the shadow of her sister Abby, who has twisted legs but an enchanted singing voice. By their magical relatives' standards, Makeda is just a "donkey"-a worthless human valuable only for her role in helping Abby survive. Tired of feeling second best, Makeda decides to move out on her own.
Makeda discovers that her new apartment building is also home to a talented rock band, and the band's leader, Brie, is a very cute boy with a distinct aura of magic about him. When Makeda's father goes missing, she must decide if she can trust Brie, or not...and her life may depend on the answer.