Jerkass Woobie: Adam. He's pretty distant with his sons and he seems to favour Conrad over Jeremiah, something they both resent for different reasons, not to mention him trying to sell the Summer House borders on a serious Kick the Dog for not only Conrad and Jeremiah, but Laurel, Steven and Belly, too. However, part of the reason he's such an asshole at this point is because he's overwhelmed with guilt and grief over Susannah's death.
The Scrappy: Belly can come off as very annoying to some readers. This is even lampshaded in the book itself.