By itself, it does nothing. But it's Paradox, so your grateful families will give birth to a stream of imbeciles, and the one decent general you'd want for your legions will be from the scorned family, with a generations old hatred and assigning him will only boost the powerbase of some old scrooge who hates half your court and rivalred already your ruler, his wife and his heir. And is not that hard, build a couple of ports and everytime there's some scorned incompetent, send them to be admiral of some useless fleet. Is very pricey in terms of gold, but stable politics and loialities are very important.