The story 'Life and Times of Scrooge McDuck' by Don Rosa retconned Grandpa Beagle and Blackheart Beagle into the same person.
Grandpa first appeared in "The Money Well" (March, 1958) where he is simply an aged chicken thief and grandfather to the younger generation of Beagle Boys. However he became a major character in stories produced in Italy. He acts as the de facto leader over his grandchildren. He tends to be the strategist of the group and has managed to find flaws in the safety measures produced by the intellects of Scrooge McDuck, Gyro Gearloose and various other opponents. Allowing him to gain entry to the otherwise impenetrable Money Bin or other secure locations. His defeats tend to result from flaws in his own methods of transporting or hiding the loot.
Grandpa has also found some success in manipulating the gullible crowds of Duckburg, both lawful citizens and the criminal element, to act in ways befitting his gang. Using public opinion and politicians eager not to lose votes against Scrooge and his allies. He has some acting abilities and at times manages to convince everyone of his apparent innocence in a crime case. Even Scrooge, typically suspicious of everyone's motives to the point of paranoia, has at times overlooked Grandpa and placed blames on others. Like all Beagle Boys, Grandpa at times employs disguises. The level of their skills at disguising is inconsistent, depending on the story, ranging from brilliant disguises to blindingly obvious ones. The Beagles are able spies and have Scrooge and his associates under near-constant surveillance. Overhearing conversations and knowing movements has not however prevented them from jumping to wrong conclusions.
As Blackheart he was a river pirate active in the Mississippi River during the 1880s. He captained his own steamboat and led a crew consisting of his three sons. He later moved to Calisota. In "A Little Something Special" (December, 1997), Blackheart operates from modern Duckburg. He convinces the younger Beagle Boys, Flintheart Glomgold and Magica DeSpell to form an alliance against Uncle Scrooge. The plan should work since they are interested in Scrooge for different reasons. The Beagles only want to loot his money, Magica only needs the Number One Dime and Flintheart the prestigious title of the Richest Duck in the World. The alliance proves formidable opponents for Scrooge but falls apart when Scrooge manages to convince Magica of a major flaw in her plan. She wants to use the dime to assume the destiny of the Richest Duck in the World. Not that of a bankrupt businessman. She has motivation to keep him as the Richest Duck. With the alliance falling apart, Scrooge was free to pursue and capture Blackheart. Magica teleported herself and the younger Beagles to Limpopo Valley, South Africa, shifting their attentions to Flintheart's Money Bin.
In Italian stories Grandpa Beagle is drawn skinnier and always smoking a pipe. Grandpa remains physically fit and has demonstrated some gymnastic skills. For example a story depicted him being about to be run over by a speeding car. He managed to avoid it thanks to some impressive leaps and still landed on his feet. He is a decent brawler but often relies on using a wooden club or other similar weapon to take out opponents.