It depends on the extent of use, Brandon.
If, say, that NPC does not frequently encounter your PC throughout his life, is not supplied by your PC, and generally speaking remains unnamed and holds no significant status anywhere, you don't need to go to the HD for addition of him to your SS thread. Furthermore, you would not need to have him approved by the domain you're located in/near.
A lot of NPC use is situational, honestly.
Take the recurring family friend example, if Jane happens to be the sister of your brothers wife who frequently comes a-knocking in your story to ask for a cup of sugar, she could be classified as a personal NPC but one who is not supplied by you or significantly provided for in any way. The NPC does interact frequently but she does not provide any sort of enhancement on your PCs life.
Another example would be Mr. Slashnhack who happens to be the cities best sword fighter. You go to him for training and he does. Slashnhack would need to be approved for use by in the city in that domains Development/Suggestion thread, especially if he frequents your threads as a trainer. Usually, in situations like that, a domain will have one for use already. You just need to check their NPC library.
This and more is broken down more informatively in the
NPC lore.