Under Phone in settings, you need to turn off "Calls on Other Devices" and under Messages you need to turn off text message forwarding, and under Send & Receive, you need to untick the iCloud email address(es).
To avoid these issues, I'd suggest setting up individual Apple ID's for each person in your household, as they're designed for 1 person each, rather than a whole family. Apple offer family options to share music and purchases etc between accounts if that's your issue.
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