yes it is possible.
You could use a state_skill, a skill which represents the status of the entity.
Example: if its control by player the state_skill is 1, if not its 0

Now in the entities while loop you have to check which state is set and if the player controls it, set the cam to it + move it by a move vector which is set via the control keys. (basic movement)
If it is not controlled by the player, you could two things:
a) just turn towards the player and run
b) use pathfinding to get near the player

Another possiblity would be, if the player changes from character A to B:
-remove player_a, remove computer_b
-create computer_a, create player_b


You could also implement "orders" so the player could decide if the other character should follow or hold his position.