Slightly related to this: while I never had enemas given by either an aunt or grandmother, I very clearly remember being given suppositories by both, as well as by my aunt's household help into the bargain (an older lady whom we also referred to as 'aunt' such and such). I know a suppository is not the same as an enema, but in many ways the circumstances involving nudity, embarrassment and body functions are very similar.
Moreover, since this was usually done just prior to being given a bath, these older ladies back then (late 1950's-early 1960's) had this apparent aversion about getting their dresses wet, so they usually took these off and went about their business dressed only in (voluminous) undergarments. As far as revealing the body, the undergarments were as useless as a normal dress, but of course the fabric, coloring and general appearance were quite different.
Why an aunt or my grandmother did this instead of my mother I really don't know. Maybe she didn't think it appropriate for her to give me suppositories at that age anymore (9 to 13). I have no idea, but I know that it happened to me. It was nothing 'wild' or sensuous of course, embarrassing yes ... but it did happen.
So I guess if those kind of relations gave suppositories, there must also have some relations who gave enemas to nieces/nephews and whatnot. Maybe also not 'wild sessions' or anything, but still some kind of enemas.
That's why I do tend to believe such stories, they can appear to be plausible as long as they don't go overboard with the sensuality. This is what I mean by comparing the stories to your own experiences.