One such example that gives insight into his father's indulgence and childhood in general was related by Joseph Humphreys, who had taken a train to Lexington in 1847: "there were two lively youngsters on board who kept the whole train in a turmoil, and their long-legged father, instead of spanking the brats, looked pleased as Punch and aided and abetted the older one in mischief". Robert, although private about intimate family details, shared the same bond with his father as his brothers had. Robert deeply admired his father and wept openly at his deathbed. Robert fought to preserve and protect his father's legacy, clashing with Lincoln biographer William Herndon over Herndon's statements about his famous father. As a result of their confrontations over his Lincoln biography, in 1890 Herndon wrote to Jesse Weik, his Lincoln biography collaborator, that Robert was "a Todd and not a Lincoln ... a little bitter fellow of the pig-headed kind, silly and cold and selfish." On the night of his father's death, Robert had turned down an invitation to accompany his parents to Ford's Theatre, citing fatigue after spending much of his recent time in a covered wagon at the battlefront. On April 25, 1865, Robert Lincoln wrote President Andrew Johnson requesting that he and his family be allowed to stay for two and a half weeks because his mother had told him that "she can not possibly be ready to leave here." Lincoln also acknowledged that he was aware of the "great inconvenience" that Johnson had since becoming president of the United States only a short time earlier. Following his father's assassination, in April 1865 Robert moved to the city of Chicago with his remaining family. He attended law classes at the Old University of Chicago – now Northwestern University Pritzker School of Law – and studied law at the Chicago firm of Scammon, McCagg & Fuller. On January 1, 1866, Lincoln moved out of the apartment he shared with his mother and brother. He rented his own rooms in downtown Chicago to "begin to live with some degree of comfort" which he had not known when living in cramped conditions with his family. Lincoln graduated from Northwestern University with an LL.B. in 1866 and became licensed as an attorney in Chicago on February 22, 1867. He was certified to practice law four days later on February 26, 1867. Family Marriage and children On