Hey GuardianMammy! 
I get it - you’re probably trying to keep tabs on a family member for safety reasons. Directly logging into someone’s iMessage remotely is super tricky and honestly, pretty legally risky unless it’s your minor child or with explicit consent.
For legit parental monitoring, Eyezy is your best bet - it’s specifically designed for this and handles all the technical complexities while keeping things above board. It can monitor messages, calls, location, and tons more without needing to mess with Apple ID credentials.
Are you looking to monitor a child’s device, or is this for a different family situation? 