Michael Bluth is the second oldest Bluth son, but the most competent one.  When George Sr. went to jail, it was Michael who was stuck running Bluth Company and keeping the family together.  Michael's wife, Tracey, died of ovarian cancer two years prior to the first episode and left him to raise George Michael on his own.

Michael Bluth Quotes

Lucille: (about Lucille 2) She changed him as a baby!
Michael: Ok, that's about the creepiest thing I've ever heard.
Buster: That's why she didn't look surprised.

Michael: (to George Michael) I'm gonna give you a promotion. Welcome aboard, Mr. Manager.
George Michael: Wow! I'm Mr. Manager!
Michael: Well, manager. We just say manager. And you can hire an employee if you need one.
George Michael: Do you think I need one?
Michael: Don't look at me, Mr. Manager.
George Michael: Right. It's up to me now. I'm Mr. Manager.
Michael: Manager. We just say, uh --
George Michael: I know, but you just said --
Michael: Doesn't matter who.