Does every local villager need Nintendo Switch Online to play online?

If I own AC New Horizons, and have Nintendo Switch Online, it is a given that I can add/remove friends as well as visit other friend's islands. However, what I want to know is this -- if I do not own New Horizons (say another family members owns it on their account on my Switch), but own Nintendo Switch Online, can I access online functions? And for other members on the island, can they use my Nintendo Switch Online capabilities if they neither own AC:NH or Nintendo Switch Online?

Solution 1:

While you would only need to purchase the game once for all local accounts on the switch (I confirmed this with a downloaded copy of the game), it appears that you do need to have an Online subscription for each account (source):

Each account is for only one Switch user

Since a Nintendo Switch Online Account hooks up to your Nintendo Account, you will need to purchase one account for every user, rather than one account per system. If you are planning to share your switch with someone else, you'd best be aware of this beforehand.