With the PublishPress Authors plugin, you can set multiple authors for each post and display their information in your site.
When you write a post, you’ll see a box in the right sidebar. Here you can choose from all the users on your site, and assign them as authors.
Using PublishPress Authors, you can create Guest Authors who don’t need an account on your site. PublishPress will treat Guest Authors identically to Authors who are linked users.
You will be able to select and display Guest Authors in exactly the same way as for registered users.