Earlier this month Nintendo finally revealed some details about their upcoming Nintendo Switch Online service. Switch owners can sign up for Online membership individually (which will link your membership to your account, not your console) or link up to eight accounts together under a Family Membership with shared benefits.
If you're considering signing up for the latter, Nintendo just sent that feature live, so you can register now. The official website makes it nice and easy to add accounts to your family plan, and you can also adjust your parental controls from that page. Once the paid membership service goes live, you can give all eight accounts on your family plan access to Nintendo Switch Online for the yearly price of $34.99.