EDITx2: I haven't updated this post in a long time. Many corrections have been offered in the comments; I'm updating now, but PLEASE READ THE COMMENTS BEFORE OFFERING YOUR OWN CORRECTION! It might already be there.
EDIT: Now public!
still_ciircee posted some
SUPER AWESOME FICBITS here and mentioned that she only knew Aiba's little brother's name. I randomly have a lot of information about their families, so!
Sho's Family
Sho's father is Sakurai Shuuji(sp?), a politician. His mother we believe is Sakurai Yuko (sp?) (Chiyo and I went on a google-fu spree), a professor of English Lit at a women's college (this was the name of a professor of English Lit at a women's college in Tokyo; I don't remember the name of the school anymore, sorry!) His younger sister is five years younger; her name is Mai, and she's done some print modeling. She works at NHK They look very similar! His younger brother Shu is 13 years younger than him. Apparently the Sakurai family have a tradition of naming their boys to all have the intials S.S. Shu is apparently a big Aiba fan. XD
Ohno's Family
Ohno's mom is awesome. Also they look very similar, apparently. His sister Mina is two years older than him; she had a baby (a girl!) in 2006, but I'm not sure if she's married/moved out. EDIT: She is indeed married! Ohno's father is hardly ever mentioned; he's a standard business man of some sort. XD They are all pretty close from the sounds of it, and Ohno spends a lot of time just hanging out with his parents. They kick his ass at Wii Bowling on semi-regular basis.
Aiba's Family
Aiba's mom is kind of amazing too. Aiba's family owns a Chinese Restaurant, and Aiba's father (Katsuhisa) is the head chef. His mom (Makio) is the head hostess. Aiba's younger brother is two four years younger, and his name is Yuusuke. He was allegedly demonic as a kid. He's in training to take over the restaurant so Aiba won't have to. Aiba doesn't live at home anymore, but he goes back to visit a lot.
Nino's Family
Nino's parents got divorced before he joined JE, but we're not sure of exact dates. He lives with his mother (who's name is Kazuko; lol with me fandom) and his sister, who is older by 2 years, has moved out (but seems to come home a lot, because again, Nino mentions her ALL THE TIME XD.) They are a really dorky family, and Nino's nikki entries about them usually have an air of OH MY GOD I AM RELATED TO CRAZY PEOPLE. It's pretty fantastic. His father is/was a professor of Japanese cuisine at a culinary school, which is apparently how Nino ended up with Kitchen Skills. EDIT: And according to a recent interview, his mother was his father's head assistant, hence how they met/ended up getting married. He described it as "forbidden love." XD By Nino's own admission, he's not particularly close to anyone on his father's side of the family, father included. His house is attached to a factory owned by his maternal grandfather that makes windshield wiper arms. EDIT: Nino is also the only boy in his generation of the family, which is also kind of hilarious. Anyone who knows The Only Boy In A Family Of Women probably gets what I mean. XD
Jun's Family
Jun is the most tight-lipped about his family out of all of them. He grew up with his mother, father, and sister (2 years older), but that's pretty much all we know. He moved into his own apartment a few years ago, so he and Aiba are the only ones who don't live with their parents.
So, yes. Everything I know about Arashi's families!