Group text messages help you to interact with many people at the same time. You just need to make a group on iphone and add people in the group text. If you find it's interesting and you want to try this feature too then here are some steps mention to add people in group text message on iphone
Steps:
Open your messaging application
Go in the group in which you want to add people
There you get ‘i’ icon, Click on it
You can find ‘add contact’ option click on it
Enter full apple id or phone number
Then finish this process by clicking on done
How to add someone to a group text message
Tap the group message that you want to add someone to.
Tap the group icons at the top of the thread.
Tap the gray arrow icon to the right of the contacts, then tap Add Contact .
Type the contact that you want to add, then tap Done.
This May Work,
Peter