When you remove a user from an organization, GitHub warns you that all their forks of the organisation's private repos will be deleted
Removing people from the XX organization will also delete their forks of any private XX-owned repositories.
And GitHub tells you how many private forks the user has but it does not tell you the repo names (even though I have permission to see them!)
It would be useful to see the repos so that I can check that they really have no outstanding, potentially useful, work left on branches (that they have not opened pull-request for).