Read manga: Kiken Junai D.N.A.

manga
Summary:

Ami has always been jealous of her little brother Chihiro, who's a popular model for girls' clothing. Now he's old enough to attend her school, and all the boys are crazy about him, even knowing he's a boy! Still, he's her brother and Ami loves him, but are her feelings for him beyond those of a sister for her brother?