How can I control multiple child characters that inherit from a main character with an AI controller?

Hello @Vettie22

You can get the blackboard component from the AI Controller and set Blackboard keys to those child characters.
For example you can set a object on the black with the parent of your character.

Then setup the behavior tick with a movement task using that blackboard key as a target.
The next tick of their behavior tree it will start moving to the target location.