Alright, in answer to my own question I did some reading on the legendary founding of Rome at Wikipedia and here's what I gathered.  It appears that the generosity of Romulus and Remus had something to do with the fact that they had been ordered to be killed as babies, after which they were set free on a raft in the Tiber River (from which they were eventually rescued).  Their beginnings, obviously, were quite humble. As they grew they eventually came to be at odds with their grandfather's (Numitor) shepherds.  After the twins killed the shepherds, they took Numitor's slaves and servants into their own company, which suggests that they took people into their company who otherwise might be considered outcasts or rejects.After Amulius was killed and the twins befriended Numitor, Romulus and Remus set off to settle down in what is the traditional city of Rome among the Aventine and Palatine Hills.  They took with them fugitives and other rejects from that group when they decided to set up their own settlement.  From there they began to accept people into their rank of similar lowly stature, and part of their governing philosophy was that the governing "Patricians" would treat their subjects as they would treat their own sons.  There was therefore a basic notion of justice that was embedded into Roman society from the beginning.  As news of this city spread, more and more people wanted to settle there.Eventually the mass influx of citizens forced Romulus (who had killed Remus in some argument) to realize that there was a serious woman shortage in the city.  It is after this that the story continues with the "bait and switch" scenario with the kidnapping of the Sabine women.  However, I think what I have stated already answers the question that was originally asked.  It was Romulus and Remus' desire to accept people into their ranks who would otherwise be outcasts that they were generous, and I think their generosity sprang from awareness of their own origins.