Gru's Mom: Shortly after you and your brother were born, your father and I divorced, and we each took one son. Obviously, I got second pick.
After the car is destroyed, Gru is knocked unconscious and Dru enters Balthazar Bratt's robot to destroy the robot's core from the inside. Once Gru wakes up, Balthazar attempts to kill him with the robot's laser and Dru destroys the core causing the robot to collapse. Gru then yells out "Dru!" and runs over to the wreckage of the robot to try and find him. The problem with this is that since Gru was knocked unconscious before Dru entered the robot, and Gru knew nothing of Dru's plan to disable the robot's core, there is no way for him to know that Dru was inside the robot.