Right; I don't believe that's really a call for a parent-child relationship; Pretty sure there has to be something tying the pictures together besides being put up at the same time like variations on an image, a series of images, sub-pictures of a larger image, or etc.
Not going to unhook these from each other just in case I'm wrong here, but it certainly doesn't seem like a precedent I've seen up until now.
Well, they all come from the same picture set on Pixiv.
Its a compilation of pics, but not all are related to each other. Artists often compile all the pics they posted on Twitter into a set on Pixiv, but not all are related. Only the last few Bleach parodies are related.