Hamlin was named after his uncle, the twin brother of his father, Cyrus Hamlin.
The twins were born in Harvard, Massachusetts, in 1769. Cyrus studied medicine at Harvard College, then followed three of his brothers to Maine, settling in Livermore.
Besides serving as town physician, Hamlin was town clerk and moderator, and representative from Livermore to the Massachusetts General Court.
In 1806, he was appointed Clerk of Courts in the newly formed Oxford County and moved to Paris with his wife and three children.
He also was probate judge and sheriff of Oxford County for many years.