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.
Maeby: Do you guys know where I can get one of those gold necklaces with a "T" on it?
Michael: That's a cross.
Maeby: Across from where?
George Michael: I have Pop-Pop in the attic.
Michael: What? The mere fact that you call making love "pop pop" tells me you're not ready.