1st. Ao, uke, is a kindergarten teacher and Kurose, seme, is the uncle of one of his students.
2nd. Midori, Ao's younger twin and also the uke, and Shortage, Kurose's older twin and also the seme.
3rd. Aki, the child from Ao's class, when he is 15 and his classmate Akane.
Kuro X Koi