The son of Sterling Lanier and Sarah V. Lanier (), he was born near
Athens, Georgia on September 22, 1819. Sterling, originally of Virginia, was a businessman in
Macon who in 1855 moved to the LaFarge Hotel in New York before losing in a fire of uninsured property that he owned. Robert himself was educated in Georgia and later in
Randolph Macon College. He studied to be a lawyer in Macon, briefly interrupting that study to marry Mary J. Anderson, later passing the bar and setting up the firm in
Griffin of Lanier & Clopton with
David Clopton, who was later a justice on the
Supreme Court of Alabama. His later law practice was the firm of Lanier & Anderson a partnership with
Clifford Anderson of over three decades. Clopton had been his college roommate from 1838 to 1840, and his marriage to Mary on 1840-10-27 in the Little Presbyterian Church of
Crewe, Virginia was a double ceremony with another of his college roommates, Clopton's cousin Burwell Kendrick Harrison of Macon, marrying Mary's aunt (only two years older than Mary herself), Elizabeth Woodson Robertson. == Military career ==