im sorry to hear your nn didn't make it...do the need to be with others to make it..i only have the one...am very sure I will get him a female this Friday...but do they HAVE to have a mate?
If you are asking if a nn can mate with other breeds the answer is yes. You will get some nn babies & some feathered necks.
If you are asking if a lone chick (only hstcher/survivor) needs a friend then that answer is yes as well. Chicks do better when they are not alone. As long as you have more than 1 chick (any breed) you are fine.