I see "upstart" as a general term for someone without much of a pedigree; nouveau riche means there is money but no 'class' and no high society family connections, other than a few new, weak ones; a parvenu, also French, is a synonym for the more British term 'jumped-up', meaning someone who is in a social class that is higher than the one he started out in. So a parvenu may have become rich himself, but his children would be nouveau-riche without being parvenus, if you follow me, because they didn't really 'make it' or 'arrive' through a significant change of situation.