“I shall very soon think him handsome, Elinor, if I do not now. When you tell me to love him as a brother, I shall no more see imperfection in his face, than I now do in his heart.”
Good heavens, I am just now, on a second read, seeing that Edward is already a kind of brother to them, though by such distant relation that they wouldn't call him that. Their half-brother John is married to Fanny, who is Edward's sister. I guess that would be a stepbrother in law -- if it's anything at all. In a later chapter he is described, actually, as "almost a relation."
In any case the terminology of their day was somewhat different, if we want to get really pedantic. In chapter 1, for example, Mrs. Dashwood, who I would call John's stepmother, is referred to as his mother-in-law; and later he is called her son-in-law rather than stepson.
I could be wrong but I don't think the novel uses the term "step". We do see terms like "half blood", "half sister", and "in law".
