Parents of YouTube's highest earner, 8yo Ryan ToysReview face legal investigation

The parents of an eight-year-old YouTube sensation are in hot water amid accusations they failed to disclose sponsored content to their son's 21 million subscribers. 

Ryan Kaji, who presents the Ryan ToysReview channel, was last year named YouTube's highest earner by Forbes, with an estimated worth of US$22 million. 

Now his parents have had a complaint laid against them by watchdog group Truth in Advertising, who say there's been a lack of transparency when reviewing sponsored toys. 

Shion and Kieu-Loan run their son's channel on his behalf, in which Ryan plays with and demonstrates various children's toys. 

The complaint claims 90 percent of the videos on Ryan ToysReview's channel include a paid-for product from brands such as Walmart, but that's not always made clear - especially for preschoolers. 

In a statement, the family said they always follow the rules when it comes to advertising disclosure requirements. 

"The well-being of our viewers is always the top priority for us and we strictly follow all platforms' terms of service and all existing laws and regulations..." the statement said. 

Some of Ryan's most popular videos, such as 'HUGE EGGS Surprise Toys Challenge with Inflatable water slide' have earned up to 1.8 billion views.