Koko wa Greenwood

From Viz:

It seems like 15-year-old Kazuya Hasukawa's life can't get much worse. Not only did his older brother marry Kazuya's first love, he brought his bride home to live with the family! Leaving his own home, Kazuya enters an exclusive all-male boarding school, Ryokuto Academy. Unfortunately, a prestigious education is little compensation for getting stuck with the cross-dressing roommate from Hell...

Note: There are more volumes in the original Japanese publication compared to the Viz release because Viz has excluded unrelated one-shots that do not involve the Greenwood characters.