We do have some suggestions for you. If you want to avoid receiving the same text messages on two devices then you can sign out of your Apple ID from one device. For more info visit https://support.apple.com/en-us/HT203983
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If 2 different users are using the devices, the best suggestion and the main recommendation is that each user should have his or her AppleID. With family share, you can have different AppleID and still be able to share most apps and purchases.
If you don't want to do that, go to Settings/Messages and there is TextMessageForwarding - click on that and turn off all devices so it does not relay.