Interestingly enough, I got an email from iCloud today (rather I was CC'd on an email to my wife). Interestingly enough, she is only using 18GB to backup her iPhone. Cumulatively we are using 95 GB between our phones and my MacBook Pro. I checked and my plan still has me on the 200GB plan. It seems to just send this email when someone gets moved from a paid subscription over to a family plan. Slight oversight on Apple's part.
Dear (Wife's name),
As requested, your iCloud storage will be downgraded to 5 GB on 06/25/2017. However, you are currently using 95 GB.
Unless you take action before your downgrade takes effect, backups to iCloud will stop, and apps will no longer be able to save documents to iCloud. You can either free up storage or cancel your downgrade to keep your current storage plan for another year.
To continue using these iCloud features without interruption, you can cancel your downgrade by selecting a different storage plan:
1.
On your iOS device, go to Settings and tap iCloud
2.
Tap Account.
3.
Tap your current plan, then choose from the options presented
For more information on managing your iCloud storage, please read this
Learn how to manage your iCloud storage >.
The iCloud Team