This is from Jean Webster's Daddy-Long-Legs (1912):
Anyway, there he was, sitting in the reception room very proper with his hat and stick and gloves beside him; and Julia and Sallie with seventh-hour recitations that they couldn't cut. So Julia dashed into my room and begged me to walk him about the campus and then deliver him to her when the seventh hour was over. I said I would, obligingly but unenthusiastically, because I don’t care much for Pendletons.
But he turned out to be a sweet lamb. He's a real human being—not a Pendleton at all. We had a beautiful time; I've longed for an uncle ever since. Do you mind pretending you 're my uncle? I believe they're superior to grandmothers.
What does Judy mean by the sentence in bold?