If I buy an individual membership, can I convert it to a Family Plan later?

Related articles

• Can I upgrade from my existing membership/plan to a family plan (or larger family plan) and just pay the difference?
• How does a Family Plan work?
• Can I upgrade from my Annual membership to a Lifetime membership and just pay the difference?
• Can multiple people use the same account?
• I currently have a membership but would like to add my family members. How do I add additional accounts?