I have been researching the family name for over six months and have found almost nothing about them. My ancestors were supposedly from Sag Harbor New York, yet records seem to not exist. Very few people of this name in the states. I have a huge family in Massachusetts, Maine and Colorado. Yet that is all I can find. If any other DeCastro's are out there and stumble upon this site please Email me with any family origin info that you may have. I still cannot determine what the nationality the name belongs too! Good luck in your own search.