iPhone - Can you add one person to an existing text thread?

Factual Questions
1

This should not be difficult but I sure cannot find the solution.

You have a two-way text conversation in progress. You want to add Aunt Tillie to it. Can you do this without creating a new group text?

Every innertube search I have conducted tells me how to add a person to an existing group chat. The method for doing this does not compute when I try to follow it for a two-way chat (press the “i” button in the top corner - there ain’t no i button. Press add member - there ain’t no add member).

I’m thinking that you just have to create a new text to accomplish this?

mmm

2

The text has to already be a group text, at least 3 (you and 2 others) in order to add or delete more people.