Use a carrier service that supports SMS forwarding or message sync
Install a third-party SMS forwarding app on the source phone
Set the app to forward incoming texts to the second phone number
Use email-to-SMS or SMS-to-email forwarding if supported by your carrier
Enable message syncing on both phones if they use the same platform account
On iPhone, use Text Message Forwarding through the same Apple ID
On Android, use Google Messages for web or device-linked message sync if available
Set up call and text forwarding features in your carrier account portal
Use automation apps like Tasker or Shortcuts with forwarding actions
Confirm both phones have the required permissions for SMS access and notifications
Test the setup by sending a text to the source phone
Keep the source phone powered on and connected if the method requires it