Will data be lost if family sharing Apple ID is changed?

This is going to be a long solution...

For a child (age varies according to country), read this support article about how to create an Apple ID for your child --> Create an Apple Account for your child - Apple Support

This support article describes how to create a new, non-child Apple ID = create an Apple Account. --> How to create a new Apple Account - Apple Support

Apple has no formal entire account merging or transferring process. The things below will help you in doing ongoing or one-time transfer of as much as possible from one account to the other. In February, 2025 Apple started allowing purchases to be migrated to a different account. This is not available in all countries. If you do wish to migrate purchases, Apple has several lengthy and detailed articles about doing this, including limitations:

- Purchases can be migrated from a secondary to a primary Apple Account to consolidate them. (This feature isn’t available to users in India.) —> Migrate purchases from one Apple Account to another Apple Account - Apple Support

- Learn about what purchases and associated content can be migrated between two accounts. —> About migrating Apple Account purchases between accounts - Apple Support

If you cannot migrate your purchases, look into using Family Sharing to continue to be able to use items purchased with one Apple account with other Apple accounts, and for some data sharing features.

- Family Sharing - How Family Sharing works - Apple Support

- Set up Family Sharing - How to set up Family Sharing on your iPhone, iPad, or Mac - Apple Support

You can use various iCloud sharing features for some ongoing data sharing.

Share folders with iCloud Drive --> Share files and folders in iCloud Drive on iCloud.com - Apple Support

Read How to use Shared Albums in Photos on your iPhone, iPad, or Apple Vision Pro - Apple Support about how to share photos.

Sharing music playlists —> How to share an Apple Music playlist on your iPhone - Apple Support

While Apple’s purchase migration documents say you cannot transfer iCloud data, you can probably still do that as a separate process. The next section may sound tricky but it lets you merge some things on a device where you have already signed in with an old account but want to use a new account and incorporate data that is already on the device from the old account. Incidentally, the data will then propagate to other devices using iCloud with that new account. (I haven't tried this with a computer but it may also work with a computer account signed into an old account.)

If you have signed into the first Apple account on a mobile device (but maybe also on a computer?) then fortunately when you sign out of that account it asks you if you wish to retain the data from the old account on your device (toggle the ones you want to on). If you keep data on the device then when you sign in with the other account it will merge this data with the account signing into the device. You can later delete individual items from the old account that you do not want. Similar information can be found in this post: I have 2 apple IDs i want to merge them h… - Apple Community , and a step-by-step in this User Tip: https://discussions.apple.com/docs/DOC-250008248 . Note that only content physically present on the device such as contacts, photos and videos will be retained. Meta data such as a game play scores that are tied to a specific account or are only on a vendor's Apple Account-specific database remotely will not be retained. Also turn off storage optimization before doing this. With Optimize Storage, smaller, space-saving photos and videos are kept on your device while all of your original, full-resolution versions are stored in iCloud. Make sure photo optimization is turned off so the full quality versions from the old account are actually on the device before merging the content into your new account. https://support.apple.com/HT205703 You can turn optimization back on again once you are fully using your new account on the device.

It used to be that apps would remain on a device and would work for a while, you would not be able to update them or redownload them unless you bought them again with the new account or download them with the new account using Family Sharing. If you use purchase migration feature this may help with this now.

Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac --> https://support.apple.com/HT208242

If this involves a device changing ownership, the person should also change the ID set in Find My. https://support.apple.com/guide/icloud/remove-devices-and-items-from-find-my-mmdc23b125f6/icloud

If another Apple account is signed in you may need to enter the password for that account to sign out of that account first.

Click on this link to learn how to 'Sign in with your Apple ID' --> https://support.apple.com/HT204053

It depends upon what you mean by iCloud data. Not all data can be shared and is exclusive to a particular account.

Shared apps will be available, but not necessarily their data.

Backing up is a good idea but what you're basically doing is signing out of the device with one account, not erasing it the way you normally would, and then signing in with the new account. This will merge most of what is on the device from the old account into the new account. Ignore the bit about migrating purchases since you are keeping the old account. Use Family Sharing to get use of the apps. You will always have to have Family Sharing set up or else the new account will lose access to the first account's apps (and apps being shared by anybody else ).

You don't want to restore from a backup otherwise it may just end up putting most things back the way they were.