Attaching a post to another post

Is there a way to attach a post (or few posts) to another post?

–more info–
I’m building a portfolio theme and I faced this problem:

The client wants to make a post entry called: ‘work01’ and another post entry called: ‘making of work01’. I want to link both images on both posts. Is there a way I can automatize this, it’s much like the next_post_link(), but the ‘making of’ posts aren’t necessarily posted in the same order, and in some cases, there are 4 making of posts.

Thx ahead ??

edit: This is the site that I’m rebuilding, you see how the making of posts are shown on the right: https://www.pixelwerks.be/hornblower1.html