Ethan's Dad, Mitchell, is Gatlin's other shut-in. He's not as creepy as Macon, but he has locked himself away in his study ever since his wife, Ethan's mother, died. The only time we hear his first name is when Amma addresses him at Thanksgiving dinner. Other than that, Ethan just calls him Dad.
Ethan may call him Dad, but Mitchell is a father in name only. Life hasn't been the same for the Wates since Ethan's mother died: "The last five months had been hard for [Dad]. He had really loved my mother. But so had I" (9.02.34). We see Mitchell so few times, he might as well be a ghost. But ghosts don't wear pajamas—we don't think.
The death of his wife is still fresh, but Mitchell can't even function. Ethan still gets up, goes to school, does his homework, and play sports. All Mitchell does is sit in his study and scribble. He hasn't written a word. His rationale? "When I'm in there with her books and things, it feels like she isn't really gone. I can still smell her" (12.19.256).
This guy is basically useless. The only practical skill Ethan's dad taught his son was how to fish—and casting a line isn't the kind of Casting Ethan needs to be familiar with. Amma does all the work, keeping house and raising Ethan. Ethan's lucky he's got her.