Well, other than Eiri and Shuichi, it's proven that Tohma is at least bi, as he has feelings for Eiri (mostly the manga). Eiri's brother, Tatsuha, is bi, though he leans more towards guys, as he is in love with Ryuichi. Ryuichi is bi, as he kissed Shuichi in the manga.
mangafox.com if you go into the directory and type in gravitation, you should find it
Yuki Isoya is 39 years old (birthdate: February 17, 1972).
Yuki Kajiura is 52 years old (birthdate: August 6, 1965).
Yuki Matsuoka is 40 years old (birthdate: September 13, 1970).
Yuki Abe is 29 years old (birthdate: September 6, 1981).
When Yuki is 15 he is 19. They are 4 years apart
"éirí" means rise / rising
Now(2012),he's 35 years old.
Which anime? There are many animes with people with the name of Yuki, but the only one I've really read is Yuki Sohma from Fruits Basket who is 16-17 throughout the manga/anime
He is roughly 17-years-old throughout the 4th season.
25!He was born on February 16 1986 :D