I'm not too sure how much of a part they could play in season 2, since there's only so many different story paths Telltale could cram into five episodes, but should they make some kind of appearance regardless?
I think Telltale could make things a little easier on themselves by having the brothers show up as walkers, with a few minor differences depending on Lee's actions in the last game. One way or another, the farm was being overrun by zombies, and it's unlikely they would have escaped even if Lee allowed both brothers to live. If Lee killed Danny, for example, we'd see Walker-Danny appear with a pitchfork still impaled through his chest. Or if Lee shot Andrew through the head instead of kicking him into the fence, Walker-Andrew wouldn't appear at all. Little details like that wouldn't give Telltale too many grey hairs, but it would still give ongoing players a treat, so to speak.