Over a dozen advocacy groups say YouTube is able to collect data on children under 13 due to large amounts of child based cartoons and childrens book videos.  Youtube is a subsidiary of Google and their Terms of Service (TOS) requires that visitors affirm they are at least 13 and hold to Google's privacy policies.  The policy states that Google has permission to collect the device location, browsing habits, phone number etc of the viewer.

The contention by advocacy groups is that tracking this type of data including profiles and behavior from a minor requires parental consent.  These protections are outlined in the Children's Online Privacy Protection Act of 1997 (COPPA.)