What organization has their children report their parents to the authorities (Thought police)?
The Junior Spies is the organization that teaches and encourages children to spy on their parents and report any suspicious behavior that might be considered unorthodox to the Thought Police. When Winston visits the Parsons' flat, he is terrified of their children, who aim toy automatic pistols at him while yelling, "You’re a thought-criminal! You’re a Eurasian spy! I’ll shoot you, I’ll vaporize you, I’ll send you to the salt mines!" (Orwell, 29). Mrs. Parsons is also afraid of her children, who are depicted as menacing, unscrupulous products of the government. In an effort to completely eradicate all political dissidents from society, organizations like the Thought Police and the Junior Spies carefully spy on the entire population of Oceania. Whenever political dissidents are discovered, they are immediately arrested and tortured in the Ministry of Love. When Winston becomes a prisoner in the Ministry of Love, Mr. Parsons is thrown into his cell and tells Winston that his children reported him to the Thought Police for saying "Down with Big Brother!" in his sleep. The Junior Spies are also eerily similar to the Hitler Youth organization during WWII, in which government propaganda was taught to children at a young age in order to create loyal followers.
The Thought Police are the organization that oversee the young spies and encourage them to report on their parents or their families but it is an outreach of a larger policy on the part of the party itself. They believe that it is important to undermine loyalty to the family in order to encourage that familial loyalty to be turned towards the party instead.
The incentive offered to the young members in terms of becoming a party member and other perks is important to again undermined their loyalty to the family and also provide reinforcement for the power of the party and the thought police.
It is indeed the Thought Police to whom the children betray their parents. This action, though, is supported by the Youth League and the Spies.