I wonder if Nick loosing his mother and father at what may have been the time he was going to start exhibiting his Grimm powers may have somehow blocked/suppressed the emergence of his powers, putting up a psychological barrier that was only finally taken down when he fell in love with and had decided to marry Julliette. This could explain the late emergence of his powers, I know we have little data to base the information off of but it still seems uncharacteristically late. Perhaps I am reading too much into the events that played out in the initial episode, but almost literally after deciding to ask Julliette to marry him he starts seeing Wesen, and the real coincidence or even a red herring was Marie turning up at the same time to announce she was dying.
Doctor: You betrayed me … betrayed my trust. You betrayed our friendship, you betrayed everything that I’ve ever stood for. You let me down!
Clara: Then why are you helping me?
Doctor: Why? Do you think I care for you so little that betraying me would make a difference?
Clara: Then why are you helping me?
Doctor: Why? Do you think I care for you so little that betraying me would make a difference?