At one point during the documentary, Gary comically leans towards the camera to faux-whisper, "This family is full of secrets." He isn't lying. A large portion of Whitney tells the story of the Houston family power struggle. Early on in Whitney's career, her divorced parents made appearances together to keep up the image of a happy family that went with Whitney's good-girl persona. Her whole family was involved with her brand and on her payroll; her brothers worked on the tour, her family "managed" her and her mother went along with them all. However, with Robyn and Bobby Brown in the picture, the battle for who had the most influence over Whitney was on.
Robyn, Bobby, and Whitney's father John regularly butted heads. Whitney's brothers openly admit to introducing her to drugs from a young age and Robyn didn't approve of all the wild partying. A few allege that John actually thought about hiring someone to scare Robyn away from Whitney, though it's not clear if this was due to homophobia or because she seemed to have Whitney's ear more than he did. Gary confirms the story, saying the patriarch didn't go through with the plan because "you never know what the outcome is going to be when you send people like that to do something."
Robyn eventually resigned as creative director after an ultimatum she gave to Whitney to choose between her or Bobby, and Whitney ended up sticking by her husband. The film goes on to allege that John soon began stealing Whitney's money, taking so much that she fell flat broke. The betrayal severed the singer's relationship with her father, so much so that she apparently didn't go to visit until he passed away.