I haven't finished the main quest yet so don't spoil things for me. I've only recently started with the institute.
So, I'm not one of those smartasses who try to guess where the story is going. I did expect my son to be older than I expected but I didn't expect that he would be older than me and that he would be the head of the institute. I love this little plot twist. I really thought the little synth boy was my son but he had been brainwashed.
The really fun part for me is the moral question. What would you do if "Father" was really your flesh and blood son? Could you really betray him? And how would you feel if your own son had turned...evil? And it's so creepy that this old man is my son!