Three years ago, YouTubers who go by Vlad, Niki, Diana and Nastya were friends cruising around Miami on a 97-foot yacht to celebrate a birthday. Today, they are locked in a fierce rivalry over YouTube supremacy.
They're not even 10.
The children are stars of three YouTube channels -- "Vlad and Niki," "Like Nastya" and "Kids Diana Show." They are the three most popular live-action YouTube kids channels in the world, with nearly 300 million YouTube subscribers between them.