Actually they act like kids, who have no real concept of what's after happening and so just continue on the way it is. To say Dave got over Bro's death lickity-split is overselling it, he was clearly affected by it in a large way. It quite probably played a large part in his desire to go out and die at the green sun - similarly for Rose (who was also affected in a very visible way).

Jade lived alone the entire time and, while she lost her doggy, she's now living with her friends. If anything she's less lonely. John also has been affected by the loss of his dad - you think Dad would've let him wander around doing nothing for 2 years? Hell no! Dad would've had him working his ass off to teach him to be a good kid.


But I think the real reason that the game chooses them that young is because their minds are too underdeveloped to actually grasp what's happened. They can't understand the magnitude of what's after going down because they have no real concept of what it was like before. They haven't lived out there - even for kids, each of them are shown to be almost completely isolated.