Miki (the heroine) is an average student who likes to play tennis, till her parents divorice and swich parteners with another divoriced couple.
The son of the divoriced couple have a child named Yuu, who is also Miki's age and very handsome. But all he does is tease her. So now she lives with her parents, stepparents, and Yuu under the same house!!
This manga and anime is very good. Has some comedy, and romance, mainly a girls manga/anime.
Ginta Shirne
Jam & Jelly it's ok, but under some parts are under constution
Kei Shirne
Marmalade Boy (This place has great info)
Marmalad Boy Encyclopedia Had good info too
Marmalade Handbook
Neko-chan's Kawaii Marmalade Boy Page
Tracy's Marmalade Boy Page Has great info on characters