From BLU:
Hired as a servant by an Aristocrat family, Claude works hard to care for the family that took him in. But when the master of the house and his wife eventually pass away, Claude must keep spoiled son Antoine in line and teach him to be a proper gentleman. As the two become closer, a forbidden love develops between them...

Shirou Kakei, a straitlaced lawyer, cooks gourmet dinners for himself and his longtime gay lover, Kenji Yabuki, a carefree, hippie-ish hairdresser. The story is told through the lens of dinner preparation.
(Source: entropy)

A single father who never had any trouble with his son discovers that his son might have impregnated his girlfriend...
Heartwarming series of short stories about a father and his son. No yaoi, but there is one story about friends of the father where we can be suspicious about their relationship. (from Possible-Soup & aestheticism)

[From Blu]:

Just before the start of the French Revolution, a commoner named Gerard pays a visit to a high-class brothel, where he sleeps with, and then buys the freedom of Jacques, a young noble sold into prostitution. Jacques looks down on commoners and Gerard has his reasons for hating the nobility, but they’re thrown together once again when Jacques ends up being hired as Gerard’s new houseboy. Jacques’ determination to make his own way in the world, and Gerard’s surprising, quirky shows of kindness slowly bring the two together into a romance for the ages!

A high school crush, a world-class pastry chef, a former middle-weight boxing champion...and a whole lot of cake!
Ono has come a long way since the agonizing day in high school when he confessed his love to handsome Tachibana. Now, some 14 years later Ono, a world-class pastry chef and gay playboy has it all. No man can resist Ono's charms (or his cooking skills!) but he has just found a new position under a man named Tachibana. Can this be the only man who resisted his charms, and if so, will the man who once snubbed the "magically gay" Ono get his just desserts? And how in the heck did a former middleweight boxing champion wind up as Ono's cake boy?

The series won the 2002 Kodansha Manga Award for shōjo.

Forced to enroll in school one month late after recovering from a serious illness, Harutaro is doing his best to remain optimistic about the entire situation. The other students are working hard to make Haru feel welcome – especially his chubby, loveable pal, Shota. However, Kai Majima, President of the Manga Club and all-around hard case, seems to be the one person intent on making Harutaro’s school life a living nightmare. (Source: DMP)

In an alternative timeline of feudal Japan, a strange disease that only affects men caused a massive reduction of male population, thus females have to pick up men's jobs, changing the social structure. Now, after 80 years of the initial outbreak and current man:woman ratio of 1:4, Japan has become completely matriarchal, with women holding important political positions and men being their consort. Only the most powerful woman -- head of Tokugawa shogunate -- can keep a harem of handsome yet unproductive men, known as "Oooku."
(Source: ANN)

From DMP:

Vol1 - Young Mr. Ida might be a newbie teacher, but he is capable enough. Problem is, every time he writes his lecture on the board, he feels this deeply intense gaze boring through the back of his head. Could he be doing something wrong?
For huge and intimidating student Kobayashi, Mr. Ida can't do anything wrong. In fact, Ida is Kobayashi's Mr. Right. That's why Kobayashi keeps giving the timid teacher looks that could kill.
Just as Ida begins to lose confidence in his teaching, Kobayashi musters the courage to clarify that the intense gaze he gives is not one of hatred but one of love. Spurred on by his feelings, Kobayashi ends his confession with a kiss. Ida doesn't push him away. All should be well. But it isn't. After all, the course of true love never does run smoothly.

Vol2 - Kobayashi, Toyo, Ida, Hashizume, and Rikuko...everyone has gotten a little older, but are they any wiser?
The loveable characters of the Moon and Sandals saga begin a new chapter in their lives. Kobayashi and Toyo have both successfully started their careers, Hashizume now heads his own restaurant, and Rikuko is studying to be a doctor. But amidst all this seeming success, old issues still lurk below the surface, waiting to be resolved. Question is, will the gang be able to muster enough maturity to finally settle old scores?