Kids tend to do OK, depending on the parents’ attitude. I have a nephew who was born with thumb and forefinger separated properly, but all other 3 digits fused. This was true of all 4 limbs.
My S-I-L went the poor baby route and tried to protect him from even knowing he had problems. Lots of surgeries, etc. I would have taught him that things happen and he can do whatever he wants to do.
He still seems to have turned out OK, although I’m sure he was teased when he was young.
Kids are naturally resilient, so I think he will adjust better than his parents, providing they encourage him to do so.
If you get dealt lemons, make lemon meringue pie!
The kid will be alright! They are young and don’t have the baggage we do messing up their thought processes.
Just don’t go overboard the other way and nickname him “Flipper”