Robert Younger was born in Harrisonville, Jackson County, Missouri in December, 1853. The Younger family supported the Confederate Army during the American Civil War. In 1862 William Quantrill established a band of guerilla fighters. The gang included Robert's two brothers, James Younger and Cole Younger.

As well as attacking Union troops the Quantrill Raiders also robbed mail coaches, murdered supporters of Abraham Lincoln and persecuted communities in Missouri and Kansas that Quantrill considered to be anti-Confederate. The gang also gained a reputation for murdering members of the Union Army that the gang had taken prisoner.

On 21st August, 1863, the Quantrill Raiders committed one of the worst atrocities of the Civil War when it attacked the town of Lawrence. During the raid Quantrill's gang killed 150 inhabitants and set fire to over 180 buildings. Frank James was with William Quantrill when he was killed in Kentucky in 1865.

After the war Robert Younger and his brothers James Younger and Cole Younger became outlaws. They joined a gang that included Jessie James, Frank James, Bill Chadwell, Clell Miller and Charlie Pitts.

On 13th February, 1866, robbed a bank at Liberty, Missouri. Over the next few tears the brothers took part in twelve bank robberies, seven train robberies, four stage-coach robberies and various other criminal acts. During these crimes at least eleven citizens were killed by the gang. As well as their home state of Missouri they were also active in West Virginia, Alabama, Arkansas, Iowa, Kansas and Minnesota.

On 7th September, 1876, the gang attempted to rob the First National Bank in Northfield, Minnesota. During the raid one of the gang shot and killed the cashier, Lee Heywood. Members of the town decided to fight back and they opened fire on the gang. Bill Chadwell, Clell Miller and Charlie Pitts were killed whereas Bob Younger, Cole Younger and James Younger, were all wounded and captured. Bob Younger was found guilty of murder and robbery and was sentenced to life imprisonment.

Bob Younger died in prison on 16th September, 1889.