Jesse James was born in Clay County, Missouri in 1847. In 1862, at the age of fifteen he joined William Quantrill's band of irregular Confederate cavalry and was involved in the fighting along the Kansas-Missouri border. He did take part in the raid and massacre in Lawrence, Kansas.
After the war, he became an outlaw and some say the old west's greatest train robber.
The members of his gang were some of the same people he had served with under Colonel Quantrill.. They were his brother Frank, the Younger boys: Cole, Bob, John, and James.
Frank James and the Younger brothers had all been boy soldiers. Frank was 18 when the war broke out and he was the oldest member of the gang. Cole Younger was 17, Jim Younger was 13, John Younger was 10 and Bob Younger was 8.
From: "Boy Soldier and Soldier Boys", Children in the Civil War Armies, by Robert P. Broadwater, Dixie Dreams Press, Bellwood, Pa.
From Civil War Talk