Which agency does the so-called main family in Idol Master specifically refer to, and how many idols are there in one party?

The Idol Master Cinderella Girls is the 346 agency, while the Idol Master 2011 is the 765 agency. There are 13 idols in one ***, Haruka Amami, Iori Mizase, Yayoi Takatsuki, Ami Futami, Mami Futami, Chihaya Kisaragi, Makoto Kikuchi, Yukiho Hagiwara, Azusa Miura, Hibiki Naha, Miki Hoshii, Takaine Shijo, Otonashi birdie.

The "Idol Master" animation is produced by A-1 Pictures. It is an animated adaptation of the game series of the same name sold by Namco Bandai in Japan. It is part of the PROJECT IM@S 2nd Vision project. It was broadcast from July 7, 2011 to December of the same year, with a total of 25 episodes. The 26th special episode will be broadcast on June 16, 2012. The decision to produce a theatrical version was announced on February 10, 2013.

The plot summary of Idol Master:

In today's highly developed entertainment and audio-visual world, girl idols have not only fulfilled the dreams of many people, but also enabled many girls who have just begun to fall in love to find the way forward in life. The small entertainment company 765 Office has gathered 12 girls with different personalities but with the same dreams.

The new man in the office serves as a photographer, tracking and recording the girls' growth every day. The producer Ritsuko Akizuki (voiced by Naomi Wakabayashi) who once was an idol patiently leads the girls step by step towards the idol hall.