Corazón was formerly an Elite Officer of the Donquixote Pirates, and the biological younger brother of Donquixote Doflamingo.
Corazón was Trafalgar Law benefactor, being the person who took the boy away from the Donquixote Pirates while attempting to find a cure for his Amber Lead Syndrome. He was able to obtain the Ope Ope no Mi, forcing Trafalgar Law to eat it and thus giving him the means to save himself from the disease.
When Trafalgar Law first met with Corazón, Corazón was noted for hating kids, especially when Baby 5 and Buffalo played practical jokes on him, such as making him slip upon passing through the doorway or giving him scalding tea that burned his tongue, resulting in his abusive behavior towards them. In fact, the first thing that Rosinante did to Law was to grab him and throw him out the window. This was actually part of an act, however, as it was his duty as a Marine to dissuade children from joining the crew, which he failed with Baby 5, Buffalo, Dellinger and Law.