Dough is a character that is meant to replace bow, Dough makes puns on chairs as he likes Stairs Bears etc.
Dough was not able to be a qualified contestant in episode 5, because Yin-Yang ate him making him the only contestant to be eliminated without any votes. In the post-credits seen in the "Lets Err R.I.P" Dough is seen as a ghost and Bow doesn't recognize him implying that toilet may have lied and that dough is not related to Bow at all. In episode 11, Bow confirms that Dough is not her brother.