There are several websites that are devoted to the life of Johnny Ringo and others that contain some notes regarding his life. A word of caution. When you visit these websites, take whatever you read with a grain of salt.
I came across websites that try to analyze why John Peters Ringo became an outlaw. Most of what is said is speculation and some of the speculation is based on leaps of faith. In particular, those sites that try to connect Johnny Ringo's behavior to a loose connection with the Younger and James brothers.
John Ringo witnessed his father's death when he was 14. This may have contributed to his having trouble with the law. However, other young people throughout history have witnessed such tragedies without turning to the life that Johnny Ringo led.
The influence of the James and Younger brothers on Johnny Ringo's life seems to be a great stretch.
Martin Ringo was a soldier in the Mexican-American War. After his discharge in New Orleans, Martin married Mary Peters in Clay County, Missouri. The two of them returned to Indiana where Martin resided prior to his enlistment. Their first born was John Peters Ringo who was born in Indiana in 1850. In 1850, Martin and Mary were living in Wayne Co., Indiana. The family moved to Missouri. In 1860 the family was living in Gallatin, Daviess County, where Martin was a merchant.
The Younger Connection
In 1864, Martin started out with his family to California to meet with his wife's sister and her husband, Augusta Peters and Coleman Younger, who were living in San Jose.
Mary Peter's sister Augusta, a widow, married Coleman Purcell Younger in Clay Co., MO in 1853 and that same year she went to San Jose, California where he had a home. Colonel Younger had moved to California in 1851.
Col. Coleman Younger's brother, Henry Washington Younger, had a son who was born in 1844 and was named Thomas Coleman Younger. Following the Civil War, this Thomas (Cole) and his brothers, James (Jim), John and Robert (Bob), formed the James-Younger gang with Jesse and Frank James.
Henry Younger and his family lived in Clay County, Missouri in 1840 and had moved to Jackson County, Missouri before 1850. Jackson County is just south of Clay County. Before 1860, the family moved south to Harrisonville, Cass County, Missouri where Henry Younger was mayor from 1859 to 1860. Henry Younger was killed in 1862. In 1870, his widow, Thomas (Cole), John, James, Robert and two daughters are living in Dallas County, Texas.
Daviess County is in the western part of Missouri a bit below the Iowa state line. Clay, Jackson and Cass counties on the western edge of the state and south of Daviess Co. It is not evident to me that Johnny Ringo had any contact with his uncles' nephews, the Younger brothers. By 1864, Johnny was in California with his mother and siblings.
The James Connection
After the death of Rev. Robert James in 1850, Zerelda Cole James married Benjamin Simms. The marriage was brief as he died in January 1854. Zerelda was the mother of Jesse and Frank James. Benjamin Simms was the brother of Frances A. Simms who married John R. Peters, Mary and Augusta Peters' father.
Coleman and Augusta Peters Younger were living in California only a few years after John Peters Ringo was born.
The James-Younger gang was formed after the Civil War. In 1864, Martin and Mary Peters Ringo moved to California where Augusta Peters Younger was living.
John Peters Ringo's family lived in Indiana and briefly in Daviess County, Missouri before moving to California.
I really don't have any evidence that there was contact between Johnny Ringo and the James-Younger gang.
Looking back at the norms of the times, in my opinion, Jesse James and cohorts were criminals. Johnny Ringo was someone who was frequently in trouble with the law and made some enemies.