Hi Avvvva, welcome to the forum.
So sorry for your loss. It's so hard to lose a pet, and to lose one so very young id an awful thing.
Please keep an eye on the one you have left for the signs of illness illusive mentioned above. Your other baby may have been exposed to something contagious.
I do believe that birds go through a grieving period when they lose a friend, just like we people do. He will miss his friend for a while. But that does not mean you have to get him a replacement.
In fact, if you don;t get him another friend to bond with right away he will be MUCH more apt to bond with you. He will see you and your family as his flockmates.
Just spend more time with him. Talk to him lots and lots. If he's not hand tamed yet, take it slow. Be patient, move very slowly around him'
You might even eat in front of him and try giving him something to eat at the same time. Birds do tend to eat as a flock so maybe he will like eating with you.
Not that he won't eat alone, he WILL. Rest assured he will eat on his own. he might be sad for a little while but with a little extra TLC he'll come around.
What are your birds names? The one that passed and the one you still have?
Got pics?? We looove pics
if you want your bird to bond with you, remove all mirrors from his cage if there are any in there. With mirrors he will bond to the birdy image in the mirror instead of you