Leadership Group is not the same as Co-Captains.
Most NRL teams have a "Leadership Group", generally senior players that set the standard for others players to follow, often a mix of forwards, backs and spine that maintain the discipline amongst the players including after hours, act as confidant when a player needs it, helps the coaching staff communicate with the players and vice versa.
"Co-Captains" are most often part of the Leadership Team, but they have additional responsibilities, such as press conferences, being the player's spokesman, negotiating with the referees on the field, they used to relay the coaches instructions on the field but the trainers do that these days, maintaining team discipline, make decisions when required and overall being the team leader on the field.
Always a Bulldog