Seiya Kou is Sailor Star Fighter, a woman from the planet Kinmoku masquerading as a Male Pop Singer of the band “The Three Lights” in quest of Princess Kakyuu. Seiya subsequently falls in love with Usagi, although she is unaware of his emotions.
Yaten Kou is Sailor Star Healer, another lady from Kinmoku and member of the “Three Lights” band.
Taiki Kou is Sailor Star Maker, as well as being from Kinmoku and a member of “Three Lights.”
It should be emphasized that the Starlights remain ladies in the manga and are never disguised as males. Only in the anime do they appear as guys and then transition into ladies.