As far as the other pups not getting sick - vaccines are a wonderful deterrent but they are not 100%. Especially in pups who have only had one or two rounds of shots. There maybe a new strain going around that is not covered by the vaccines, or it may be that they were not yet fully immune. Many years ago we had a litter of pups -- all of them were fully vaccinated, and the adult dogs at the same time. My neighbor had one of the pups, and he came down with parvo when he was about 10 months old - the pup we kept and all of our adult dogs were fine. He recovered well, and that is the only case of parvo I remember hearing of.
I'm sorry for your sad loss. Get lots of puppy kisses from the others... it wont make it all better, but it wont hurt either.