No, his great-grandfather was a schoolteacher and entrepreneur.
Yes, he did. Nichols, in fact. Then Yale. He was a director of Marine Midland at the age of 23. The sort of position that only wealth gets you at that age.
The Knoxes were not poor, and Seymour III was no self-starter (nor was II). IV is a bit of an enigma; the family fortune has been protected from his hands.