That Robert Stewart, the only son of Marjorie Bruce, became Robert II was the conclusion of a chain of unlikely events. His initial survival was almost miraculous, for he was delivered by Caeserean section from the body of his mother, who had died of injuries after a fall from her horse. 
When he was two years old in 1318, he was acknowledged as his grandfather's heir, a position he forfeited in 1324 on the birth of the future David II. Forty-seven years later, when against all expectations David II had failed to perpetuate his dynasty, Robert II was crowned and anointed at Scone on 26 March 1371. 
Perhaps a man advanced to supreme power by the delayed action of chance could not have been expected to be a very decisive ruler; but it was unfortunate that, by the standards of his time, he was well past his prime and in poor health, so that he lacked the energy required of a king responsible for every aspect of government.

Source: Leo van de Pas