i key all missing people as self, and all other mentoned persons with there relation mentioned, if it says its the daughter of some one so we should key them as daughter.
onece i had somthing like : missing ellen mcXXXXX wife of thomas xxx, and another person was missing. the husband were just normal letters, so not missing so i keayed them as husband directly under there wifes.
it is in the thing it self that every body who is a mother off someone, also is the daughter of some one and maybe also a sister. i think key as daughter is more important then sister, because its a directer line.
and don't forget what will happen later to those things. later this things will besearchable her like many things before, and when you found a name of your anecstors and finding it in this textes you will mostly red the text and then you can find out yourself that some have also some ssters or brother or even uncels and aunts etc.
i think important is that its keyed.