How can I achieve this:

 TODO-state should automatically change to DONE when I have checked-off both 'John' and 'Jane' ?

1. The manual showed me how to do this if John and Jane are also TODOs: using org-after-todo-statistics-hook.

I just can't find the check-box equivalent.

2. Google turned up 'org-enforce-todo-checkbox-dependencies' - but that is only half of what I'm looking for.

If this feature does not already exist, I'd like to suggest this as a useful enhancement.