I believe your answer can be found here.
Cancel Premium Individual Plan
Paid Organizations (Families, Teams, or Enterprise) automatically provide all users with access to premium features. If you had a Premium Individual subscription at the time of creating the Organization, you can cancel your Premium Individual subscription without losing access to premium features.
Bitwarden offers refunds for cancelled Premium Individual plans within 30 days of account creation. If you create a paid Organization within 30 days of creating a Premium individual account, Contact Us to initiation your refund.
At this time, Bitwarden does not offer refunds to paid subscriptions older than 30 days.
It would appear you can be refunded a personal premium plan if upgrading to a premium organization plan instead as all members of a premium organization will also get premium for their personal vault.
Family Organizations will only be fixed at 6 user licenses, so if someone has premium and is also a member of the family org it will still count 1/6 of the spots.