I think such a definition is just too broad. Just because he doesn't live up to the most attractive view of liberal meritocracy shouldnt define him as a "failson". He's certainly a goofus and his stans are really pitiable, but he's not living solely on his family name, he's not failing, he's not the kid who hid from the family at Thanksgiving or who takes a job at his daddy's company and just sits there with his dick in his hand.

Eric Trump, getting his hand held by all his father's people, pretending to do business things all day-- sure failson. Koch brother scion, a huge loser, who was given money to run his own absurd garish shirt company, which certainly runs in the red, is a failson. Hunter, failing at every endeavor, needing a constant stream of handlers to avoid embarrassing his father, failson. AJ soprano, archtypically failson. Making the best of wealthy networking and schooling, wild success in business: that's just the way of the world.