What can I do about someone breaking into my email account?

I bought my child an ipad. He took it to his dads house. The child communicates to me through this device. The dad went into the device and broke into the email address I put on the device and changed the recovery password and login password. I dont know how they got the password. My child does not know. I got a notification from google that this happened and at the location of where there house is. My child is a minor (7 years old), so technically the email belongs to me. Thats invasion of privacy. He didnt even ask me permission to do that or explain why.

A few years back that same person broke into my email and it was recorded in our custody report that this is illegal because they broke in and also took documents.

What should I do? Take this up with the court system and sue? Do I have a case?

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