Isaac Harper was 44y in the 1850 United States Census for Reading, northwest ward, Berks Co., PA. His estimated birth year is 1806. His wife is Sara, also 44y old.
Children are Caroline, Lewis, James B., Daniel, Martha, Sally and William. Elizabeth Harper is 70y and I assume that she is Isaac's mother. Another person, is Elizabeth Otto, 70y. Everyone in this household was born in Pennsylvania.
Does this look like the right Isaac Harper to you? I'm guessing that his father was nearby when Isaac was born, but I don't have the answer as to his first name.