My dad and I used to have the same Apple id, but recently I made his own (he didn't know how to work his) and I changed it on his phone. I kept mine on a new device. But he still keeps getting any app that I download. I don't know how to make it stop transferring all my data to him.
Your Dad's phone is still tied to your Apple ID for automatic downloads, so any of your purchases are automatically downloaded to his phone. This is easily fixed, and can even be done without access to his phone.
You can manage your automatic download devices with iTunes. Launch iTunes (these instructions are for iTunes 12.x), make sure you're signed in to your Apple ID, then:
- Click the account dropdown in the title bar, to the left of search (it'll be labelled with the first name of the Apple ID).
- Select Account Info (you'll probably be prompted for your password; make sure you login with your Apple ID.
- In the section labelled iTunes in the Cloud, click the Manage Devices link.
- All devices authorised for automatic downloads, whether they're currently set to receive items or not, are listed. Remove any unwanted devices by clicking the remove button next to their entry.
- Click Done, 'cause you are (done).
Any devices you removed from the list will no longer be able to automatically receive purchase you make with your account. If you remove a device within 90 days of adding it to your account, that device cannot be added to another Apple ID until the 90 days have passed; in this case, the device's entry will show the remaining number of days.