Oh yeah, interesting backstory for Beit.
Minori: The idol fanboy. His uncle (I believe, got that from jpwikipedia) was murdered by a gang of men which all of them were turned out to be idols. After that, Minori puts his uncle's idol magazines featuring him in boxes and look at the picture of said uncle, wondering what he thinks of idols and wants to find out the answer by becoming an idol.
Kyoji: His father called him a failure when he saw the rejection letter. He ran to his bedroom, packing up his belongings and his brother showed up, calling him a loser for running away from his well-established family as he blocked Kyoji's punch with his hand. Afterwards, Kyoji swores that he'll succeed without his family's name.
Holy carp, iM@S! Since when did you become so violent and depressing?
What did Minori's uncle do to them? Exposing scandals?
Looks like SideM is getting some new characters.

http://imassidem.blog.fc2.com/blog-entry-192.html
People are spreading interesting rumors that they could be the SideM siblings jumping the bandwagon.

According to this Japanese twitter post I found, this is a list of all the siblings the SideM idols had. (Tsubasa's little brother aside...)
Kaoru -> an elder sister
Hideo -> 2 elder sisters, 2 little brothers, and a younger sister
Seiji -> (
seldom mentions his siblings?) At least, we know he has a niece.
Shiki -> an elder sister
Hayato -> an older brother
Rei -> an elder sister
Shouta -> 2 elder sisters
Hokuto -> a little sister
Yusuke -> a younger brother (That would be Kyosuke)
Kyosuke -> an elder brother (That would be Yusuke)
Shiro -> an older brother
Kanon -> a younger sister
I don't know what to think of this mysterious trio idol unit. But from what I know and my Japanese friend who has been leaking this info, they plan to reveal who they are next week.