The entire story comes down to one thing and it's not the conservatorship. From ESPN.com.
According to the legal filing, the movie paid the Tuohys and their two birth children each $225,000, plus 2.5% of the film's "defined net proceeds." The movie became a critically acclaimed blockbuster, reportedly grossing more than $300 million at the box office, and tens of millions of dollars more in home video sales. The film received an Oscar nomination for Best Picture, and Sandra Bullock won a Best Actress trophy for her portrayal of Leigh Anne Tuohy. While the deal allowed the Tuohys to profit from the film, the petition alleges, a separate 2007 contract purportedly signed by Oher appears to "give away" to 20th Century Fox studios the life rights to his story "without any payment whatsoever." The filing says Oher has no recollection of signing that contract, and even if he did, no one explained its implications to him.
The deal lists all four Tuohy family members as having the same representative at Creative Artists Agency, the petition says. But Oher's agent, who would receive movie contract and payment notices, is listed as Debra Branan, a close family friend of the Tuohys and the same lawyer who filed the 2004 conservatorship petition, the petition alleges. Branan did not return a call to her law office on Monday.
So Oher apparently did sign away his ability to profit from the movie (not sure why he would have done this). His agent was Branan who knew the Tuohy's, but I don't see how this impacts them at all. It seems the real villian here would be either 20th Century Fox or Branan. Or Oher is just a moron.