Carloman abdicated Italy to the great-grandson of who?
Charlemagne
Title: Charles the Fat
Passage: Charles III (13 June 839 – 13 January 888), also known as Charles the Fat, was the Carolingian Emperor from 881 to 888.  The youngest son of Louis the German and Hemma, Charles was a great-grandson of Charlemagne.  He was the second-last emperor of the Carolingian dynasty and the last to rule, briefly, over a re-united Frankish empire.
Title: Louis the Younger
Passage: Louis the Younger (830/835 – 20 January 882), sometimes Louis III, was the second eldest of the three sons of Louis II the German and Emma.  He succeeded his father as the King of Saxony on 28 August 876 and his elder brother Carloman as King of Bavaria from 880 to 882.  He died in 882 and was succeeded in all his territories, which encompassed most of East Francia, by his younger brother, Charles the Fat, already King of Italy and Emperor.
Title: Carloman of Bavaria
Passage: Carloman (German: "Karlmann" , Latin: "Karlomannus" ; c. 830 – 22 March 880), was a Frankish king of the Carolingian dynasty.  He was the eldest son of Louis the German, king of East Francia, and Hemma, daughter of a Bavarian count.  His father appointed him margrave of Pannonia in 856, and upon his father's death in 876 he became King of Bavaria.  He was appointed by King Louis II of Italy as his successor, but the Kingdom of Italy was taken by his uncle Charles the Bald in 875.  Carloman only conquered it in 877.  In 879 he was incapacitated, perhaps by a stroke, and abdicated Bavaria to Louis the Younger and Italy to Charles the Fat.
Carloman of Bavaria Charles the Fat