Hi iphoneproblems99,
Thanks for coming to Apple Support Communities for help today.
We can only advise switching on Messages in iCloud on all devices. The intent of the feature is to sync Messages to all devices: Use Messages in iCloud.
"When you turn on Messages in iCloud, your message history is updated automatically on all of your devices. That way, you always have the same view everywhere you use iMessage. When you delete a message, photo, or conversation on one device, it’s removed from all of your devices. And since all of your attachments are stored in iCloud, you can save space on your device.
You can use Messages in iCloud on your iPhone, iPad, iPod touch, Apple Watch, and Mac. For your privacy, Messages in iCloud is end-to-end encrypted, which means you can't view or access Messages online via browser."
Have a fantastic day!