I have a relative that recently got employed with a government run agency. Not super high clearance, but he had to supply all kinds of info about his parents, his birth, his residences...but, the President of the United States—nah!
I was just discussing this the other day. The men in black not only investigate every detail of the person's life but also his parents, siblings, spouse, kids, etc. There's no stone that's left unturned. The only exception to this rule seems to be The Won.