The way I understand the instructions, all the people who are listed in capital letters are "Self" and the ones listed in mixed case are keyed as their relatives. If John, Mary and Catherine are all in caps in your example I would key John - self, Ellen - daughter, Mary - self, Catherine - self, so that Ellen has the right parent.
Sometimes there will be the name of the spouse or other relative of other people shown in caps after the
first one, and if we only keyed the first person in caps as self and the rest of them by their relationship to the "self", we would have to miss some of those relatives out.
But I would love it if WAP could give us a definitive ruling!