Can I auto forward texts to another phone number. Bothe users have iphone.

With the limited information that you have provided, I had to guess the problems faced by you. Some of it can be understood by reading below

If you want to keep two iPhones independent of each other then best would be to have two different Apple IDs.

Otherwise, there are basically three types of sharing

1. Text Message and
2. Calls on the other device

iCloud Photos & Messages: iCloud now keeps your entire messages history updated and available on all your devices — even when you set up a new device. Learn how to keep all your messages in iCloud.

1. Set up text message forwarding
   1. On your iPhone, iPad, or iPod touch, go to Settings > Messages > Send & Receive. On your Mac, open Messages, choose Messages > Preferences, then click iMessage. Make sure that you're signed in to iMessage with the same Apple ID on all your devices.
   2. On your iPhone, go to Settings > Messages > Text Message Forwarding.*
   3. 
   4. Choose which devices can send and receive text messages from your iPhone. If you're not using two-factor authentication for your Apple ID, a verification code appears on each of your other devices: enter that code on your iPhone.
   5. 

Both Apple IDs need to be the same.