He is also the brother/sister of the player character (Cole or Ella).
In the games
Wade appears at first when you arrive in Waytide City and meet your rivals. He introduces the player and Rodney to Misty, and says he will challenge you when you obtain 7 gym badges.
After this, He appears as the leader of Waytide City's Gym. This gym is the eighth and the last to be challenged by the player. Trainers who defeat Wade will receive the Torrent Badge, along with TM105 Ripple Wave.