If you're looking for manga similar to Korogaru Kyoudai, you might like these titles.
When a boy's divorced mother returns from America, she brings a blonde haired girl. "She is your sister," she says, and we are going to live together.
Follows an aspiring manga artist and her older brother. The story begins when the sister's work wins the Rookie of the Year award. Even though she should be happy, for some reason her face is sullen. Is she hiding a secret?
The Shinamoto Siblings love themselves more than anything else. This story is also about the mysterious Aisato Siblings. Because these two sets of siblings are similar, it's natural that the boys and girls are friends with one another. Even though they may seem to think "only of themselves," their life motto is that "those of a flock must stick together". It seems that these two sets of siblings give off an otaku-lifestyle!?
Youichi's a gruff, taciturn boy who attends a school full of delinquents; Chikage is naive, friendly, and student of a prestigious academy. These two very different boys become stepbrothers and suddenly find themselves living under the same roof.