I have had 2 pekin ducks that have been together since they were hatched, never seperated-?

but i had the female pekin duck die because it was attacked and killed by an unknown animal (i kept them both outside in a pen, but now the male pekin duck stays inside with me). i have now gotten a baby 2 week old muscovy male who my male pekin duck isn't getting along with. i put them close together and my pekin duck hissed and snapped at the little one. what can i do to make them grow closer and bond? every little advice i can get would help, thanks.