Fans are left wondering why Justin Bieber has unfollowed his longtime mentor and close friend Usher on Instagram, with some speculating it could be due to a "big" reason.

Almost two decades on, Justin appears to have quietly cut ties with his former mentor Usher, 46, so we look back on their close 17-year friendship. Usher didn’t discover Justin but he was there early on in the Yummy singer’s career, having been brought on board immediately by Scooter.

The recent decision by Canadian singer Justin Bieber to unfollow his former mentor and friend Usher on Instagram has generated great concern among his fans, unleashing speculation