The Impeachers: The Trial of Andrew Johnson and the Dream of a Just Nation by Brenda Wineapple:
If Johnson could control his drinking, his two eldest sons could not. Charles, the eldest, an affable young man remembered as kind and loveable, went on such a wild bender during the Democratic convention in Charleston in 1860 that his younger brother Robert had to hustle him quickly out of town. Three years later, when Charles was thirty-three, he fatally fell or was thrown from his horse. The word was that he’d been drunk. By then, Robert too had a problem. In 1850, at the age of twenty-four, Robert Johnson had successfully run for the Tennessee state legislature, and during the war, he raised a regiment. But he had a reputation for inebriation, and though drinking in the army usually passed unnoticed, General Rosecrans warned Andrew Johnson that his son’s alcohol consumption had “become a subject of remark everywhere.”
In the spring of 1863, Robert did fight admirably against an Alabama cavalry of about two thousand men and apparently took fifty prisoners, but the following fall, his father, disgusted by more reports of Robert’s drinking, made him resign his commission. “I have said and now repeat that I feared you would be dismissed from the Army unless you reformed and took Command of your Regiment and give Some evidence of determination to Serve the country as a sober upright and honorable man,” Johnson told his son. Robert said he’d do better: “The intoxicating bowl goes to my lips no more,” the young man promised. But a pattern had been set in motion: Robert would swear off liquor, his parents would believe him, then he’d backslide. In the spring of 1865, he wasn’t even sober enough to understand that President Lincoln had been shot.