Help! What is the name of this manga?

A boy dresses up as a girl, so he can attend the same school as his sister. The drawing style is similar to Marmalade Boy. I don't know if it's ever been published in English.

Sounds like "Mint na Bokura" by Wataru Yoshizumi, who is the same person who did Marmalade Boy. It features male/female twins, and when the sister goes to a boarding school, the boy dresses up as a girl and goes so he can be with her. It's never been licensed in English.

Yeah, that's Mint na Bokura, and it has not been translated into English, sadly. I'm fairly certain it is (or was) available in Spanish at one point along the way.

Thirded that it's Mint na Bokura

It's available in French! I even have it :3 It's really cute (awwww...I want more French manga...they have some different stuff out than here in the states and it's cheaper)