Stories have a habit of mushrooming and expanding out, which one article can’t handle. The follow-up article continues the story.
A follow-up article should follow on from the first story logically. But, sometimes, it’s a different story about the same group and people. However, this isn’t really a follow-up article, as technically, a follow-up should have a clear link back to the first article.
The other kind of article, where there’s another kind of story about the same group of people, an individual, or an issue, is really a separate article rather than a follow-up. But it could be complimentary, as it does continue the history of that group, individual or issue, that has been recorded and set down. It’s just not the same story.
In my experience, I wrote three articles about a small television station. The third story was a follow-up article from the second, but the first article was about something else, although was the same group of people. But I think the second and third complimented the first.