Parents are of course free to log in to their own account on a device and then allow their children to access it. However, you are then solely responsible for this. Because in such a constellation, there are no protective functions for minors that safeguard your child from adult content and advertising that targets adults. And you should also think twice and consider using the Parental Controls filters in Family Link or YouTube Kids to protect your child from bullying, privacy violations, and access to children through sick, greedy, hateful, or otherwise critical contacts. And then there's probably a limit to that at one point. If you give your children completely uncontrolled access to Google services, YouTube, and other social media accounts, such as Instagram, Facebook, TikTok, Snapchat, WhatsApp, etc., and the child gets disruptions or problems as a result, this will certainly be an issue to be discussed with the youth welfare office at some point. Therefore, responsible decisions are absolutely necessary here, for the welfare of the child and not only for "I want to have my silence, go away, watch YouTube".