Siblings disagree in Irene Hunt’s 1964 lovely, timeless novel, “Across Five Aprils.” In the story, Kentuckian Jethro Creighton comes of age during the American Civil War; his reckoning begins at the family dinner table. There, his older brothers argue about the conflict dividing the country. Two brothers, Tom and John, the ardent abolitionist, plan to fight with the Union. The other brother joins the Rebel army.