First of all congrats and i think i can help you as i have adopted a child.
Mostly what you need to do is treat this boy the same way you treat Seth and Elliot, show him there is no difference between them.
Be supportive and just be very patient, you'll need a lot of patience (belive me).
That's the best advice i can give you.
If you have any other questions feel free to Personal Message me i'd be really happy to help you
