Yep, and no need for him to do so. The family setup allows a child account as well. I don’t have experience with how those work, though all of this overall only applies to the content through iTunes or other Apple stuff.

If it’s another app/service offering the kids content, all of this is moot and it’s however the app handles it. Netflix and Hulu for example have their own ways of setting up multiple user profiles on one account, and it asks “who is watching”.

If my partner wants to watch a movie I bought on iTunes, or is perhaps available by our HBO subscription, they can search for it via Siri or the Search app on the home sceeen. It plays, no matter who’s iCloud profile is signed on, or which AppleTV we are using. The iCloud profile switching is the closest thing to a “who is watching” when using the TV App, so we can individually use that to track what we are watching across Hulu/iTunes/etc...

Here’s a link explaining it better and with photos of how to set it up. This might be from an older tvOS release, so the UI may not match exactly now: https://www.imore.com/how-set-multiple-accounts-your-apple-tv