According to the book, son Oswald Freeland was born in Canada after the family arrived there in 1821.
The only document I have found that mentions him by name is an 1851 U.S. Passport application (referenced in the family history). This is the oldest passport application I have in my family database.
NARA Series: Passport Applications, 1795-1905; Roll #37: 23 may 1851-30 Sep 1851. Record for Oswald S. Freeland, 1851.
Some of this handwriting is challenging to read, but I can read the description: Oswald S. Freeland is 28 years old; 5 feet, 10 inches tall; with a hight [sic] + broad forehead. He has dark blue eyes, an ordinary nose, a "rather large" mouth, and a long chin. He has brown hair and a light complexion. The most descriptive (I think) is that after face is "long with moustache + whiskers."
He applied for the passport in New York City on June 7, 1851, stating that he was born in Canada and is a naturalized citizen. I don't know if he naturalized or if he became naturalized as a minor when his father naturalized, but I haven't found a record for either.
As of now, I have found no other record for my 3rd great uncle Oswald Freeland, which makes me wonder if he traveled to settle outside of the U.S. or if he died during his travels.