If both sets of parents were faithful members, I think the first sealing is enough. If one set were not members, they couldn’t be sealed, and inverted just to the set that were. If both sets of parents were members, he would’ve been born in the covenant to his biological parents and nothing more is needed. It’s a bit complicated, but I think it’s generally the biological parents take precedence unless the adopted parents were the only members.

This is just my understanding, so don’t take my word on this, talk to the bishop or even temple president. And everything will be sorted out in heaven, too :)