There aren't as many manga out there about brothers as there are about sisters, but a series like this doesn't make the best case for why there shouldn't be more.
ME & MY BROTHERS (Onii-chan to Issho), by Hana Tokeino. First published in 2004 and first published in North America in 2007.
PLOT:
Sakura had been orphaned at an early age, and age 14 she was orphaned again when her beloved grandmother passed away. Shortly thereafter, her quiet home is invaded by four strange young men who immediately declare themselves to be her brothers. They are in truth her former step-brothers, who were separated from her upon the death of her parents when Sakura was an infant. Now they want to make up for lost time, but can Sakura deal with the challenges that come with having four very overprotective guardians?
