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.
Lucille: I'll be in the hospital bar.
Michael: Uh, you know there isn't a hospital bar, Mother.
Lucille: Well, this is why people hate hospitals.
Michael: He's not a chicken. He just doesn't like confined spaces, that's all.
Gob: I thought it was open spaces.
Buster: No, it's both.