I would believe he was born in Mobile City, Alabama where his father was recorded in the 1840 Federal census

1860 United States Federal Census about Thomas Emanuel
Name: Thomas Emanuel
Age in 1860: 23
Birth Year: abt 1837
Birthplace: Alabama
Home in 1860: Mobile Ward 4, Mobile, Alabama
Gender: Male
Post Office: Mobile
Value of real estate: $ 100,000 Pers. Estate $ 60,000 Father Johathan
Household Members:
Name Age
Jonathan Emanuel 60 President Ins. Co. born in England
Isabella Emanuel 40 born in New York
Thomas Emanuel 23 Clerk
Josephine Emanuel 18
Nena Emanuel 15
Edwin Emanuel 13
John Donald 35 Coachman
Benie Jones 30 Female, Servant

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1840 United States Federal Census about Jonathan Emanuel
Name: Jonathan Emanuel
Township: Mobile City
County: Mobile
State: Alabama
Ancestry.com