whenever I change the details of a contact on my daughters iPad it changes the details for that contact in my iPhones things like nicknames keep changing.
We are using family sharing on my Apple ID but she has her own iCloud logged on to the iPad.
I have checked accounts and my ICloud isn’t signed in anywhere.
iPad Air, iOS 12
Hello,
An Apple ID is meant for just 1 person’s devices meaning that you should not be sharing an Apple ID with their iPad. Checkout this Apple Support document on how to setup their own Apple ID. You would then restore the iPad to factory settings and set it back up with their Apple ID.
Family Sharing and Apple ID for your child - Apple Support
Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
How to stop contacts on my daughters iPad changing contacts on my phone
