this is absolutely more Serious then the sort of ask i usually get and realistically i haven't had to deal with this in nearly a decade (wild, time flies).
in my experience it can actually just Take A Bit. the parent being well-meaning and supportive absolutely helps, and also makes it easier (although this is VERY dependent on other factors that you/your nephew will know better than i possibly could) to have a frank conversation of "i know it's hard, i believe you that you're trying, but it still hurts to have you get it wrong this often and i need to reiterate how important it is to me that you keep making the effort." hit 'em with the old "i'm not mad, i'm disappointed." again, very very dependent on how the parent actually is. worked for me but ymmv.
good luck, congrats to your nephew. you can tell him that the ceo of some bug-themed social media platform thinks he's doing great.

