Endar kidnapped the boy.
And Picard justified the kidnapping by returning the boy to Endar. Picard set a bad precedent where aliens may believe that they can attack and kill human colonists and then kidnap their orphaned children with impunity.
Jono's biological grandmother must have been mightily pissed at Picard. She had every right to be.
Jono's wishes should not have been the only factor in determining where he should have ended up imho.
There was child custody case in a DS9 episode called "Cardassians". The two situations are not exactly the same, but in that instance the Cardassian teenager whose custody was in dispute was returned to his biological Cardassian father, even though he had been raised by his adoptive Bajoran parents.
The Cardassian kid wanted to stay with his adoptive Bajoran parent. It was not the kid's wishes that were the sole or primary determination of where he should end up. There were other important considerations. After a hearing, Sisko ordered the boy to be taken from his Bajoran family and returned to his biological one.
But, the Cardassian boy demonstrated self hatred for being a Cardassian. He and the other Cardassian orphans were raised to despise all things Cardassian. They were taught Cardassians were evil. Imo, this are decidedly different circumstances.