Character Analysis
Say "Uncle"
As you can see, the general theme here is that we don't really know anything at all about any of these characters, even our narrator.
However, Miles and Flora's uncle really takes the cake when it comes to being shady and mysterious—we don't know his name, what he looks like, what he does, or what any of his motives are.
All we know is the he's wealthy and handsome, and that these things alone win the Governess's heart from the moment she meets him:
This person proved, on her presenting herself, for judgment, at a house in Harley Street, that impressed her as vast and imposing – this prospective patron proved a gentleman, a bachelor in the prime of life, such a figure as had never risen, save in a dream or an old novel, before a fluttered, anxious girl out of a Hampshire vicarage. One could easily fix this type; it never, happily, dies out. He was handsome and bold and pleasant, offhand and gay and kind. He struck her, inevitably, as gallant and splendid, but what took her most of all and gave her the courage she afterward showed was that he put the whole thing to her as a kind of favor, an obligation he should gratefully incur. She conceived him as rich, but as fearfully extravagant – saw him all in a glow of high fashion, of good looks, of expensive habits, of charming ways with women. (Prologue.13)
Dang. No wonder the Governess is a smitten kitten.
But after this glowing (and lengthy) description, the Uncle is never seen again. Oh, Uncle: we hardly knew ye.