On the new Apple TV, if logged in an account with Family Sharing for which "Ask to Buy" is enabled, when you "Ask to Buy" an app which is only available on tvOS (that is, not on iOS) and the parent opens the "Ask to Buy" notification on their iOS device, they will simply see a blank white screen with a "Cancel" button. The "Decline"/"Approve" buttons and the App Store listing never appear. As such, there is no way for the parent to approve the "Ask to Buy" request on iOS.
One of our users wrote in to us about the problem, said she spoke on the phone with Apple for an hour, and they told her it was *our* fault! I've filed a bug report for this issue so hopefully that gets resolved ASAP but in the meantime I'd at the very least like Apple to know about the issue and tell customers that it's their fault, not the developer's.
The current workaround is that the parent can approve the request from an OS X device. The App Store listing still never appears but the "Approve"/"Decline" buttons do.