I want to remove my (now) adult son from Family sharing. What happens to apps and subscriptions HE purchased?

If he purchased the apps and subscriptions they belong to him not you even if you paid for them.

Once he is removed from Family sharing all the subscriptions he started and all the apps he purchased will stop being shared with you. He will continue to have access to anything he purchased and the active subscriptions he started if he is able to pay for them otherwise they will pause until they can be paid again.

You will lose access to any apps he bought and any subscriptions he started though.

That refers to data on the devices. It won’t be syncing any more data if the subscription is not active.

Anything already in iCloud would eventually be removed. Apple simply cannot store billions of terabytes of data of people that aren’t paying for the storage.

They also state the following in their downgrade kb article:Downgrade or cancel your iCloud+ plan - Apple Support

Before you downgrade or cancel your iCloud+ plan, first download or remove content that exceeds your new storage amount. To make sure that you don't lose any information

Unless you have your own subscription to iCloud, yes you may lose access to all data.

You should be able to start an iCloud subscription yourself from Settings on one of your devices before you remove him from your Family Sharing group to retain all your iCloud data without interruption.

The subscription you get, will be added to the one he started while he remains in thew family group, then once you remove him, you will retain your own iCloud subscription.

corny40 wrote:

What would be the best way to go about transferring that cloud data?

No transfer necessary if done as explained above.

Make a backup on a computer (can you still do that?), then purchase our own cloud storage and then backup that backup on the new cloud?

You can backup to a computer. The option has never gone away. But you cannot just transfer that backup to iCloud.

Easiest way is to just start your own iCloud subscription while he's still part of Family Sharing. That way you guarantee a seamless transition.

click here ➜ Buy iCloud+ or upgrade your current storage plan - Apple Support

Unless you have your own subscription to iCloud, yes you may lose access to all data.

According to Apple:

Downgrade or cancel your iCloud+ plan - Apple Support

● If your iCloud storage exceeds your new storage plan capacity, iCloud won't sync or update your information. iCloud updates again when you increase your storage capacity or delete information to make more space.

I guess it depends upon what they mean by "won't sync". To me it is not actually deleting the files, just putting a lock on them so they don't transfer. Once you upgrade again they are still there. That's my interpretation of it.

Crazy, me too w adult kids, im paying and I lose access, I get it now! Lol