Gotcha. So essentially, in lieu of a background's normal properties (usually skills, tools proficiency, language), you can have a custom background that grants one of those feats. I think that's fine, since the Planescape book introduces the same character options, with the similarly-structured Gate Warden and Planar Philosopher feats. Approved.
No, these must be three discrete individuals. If you scan the original recruitment post, you'll see a range of approaches applicants took. Some made all 3 the same class with different subclasses, others three characters with the same name, some all the same race, etc. The association just needs to be thematic/fluff.