A Microsoft file hosting and synchronization service.
Sorry, I wasn't notified earlier of your last reply.
I hope this helps: Switch between Microsoft 365 subscriptions
You share your Microsoft 365 subscription with another person or another Microsoft account that you may own, not with another device. A device, like a computer, can have multiple individual accounts, each with unique sign-in credentials.
Share your Microsoft 365 Family subscription
"Do I uninstall the Personal license and then share a license from the Family?"
You can cancel an existing license (subscription) on your Microsoft account.
The software to install (the Microsoft 365 apps) is the same regardless of whether you are on a Microsoft 365 Family or a Microsoft 365 Personal plan. The license is for your account (accounts) or other family member accounts, not devices. If you so desire, you can uninstall Office and then reinstall using the link in your Microsoft account.
"Will all docs and emails etc be retained on the Personal laptop if I do so."
Your account, emails, and data will remain unchanged.
Do you have some other version of Office, other than Microsoft 365, installed on that computer?
Would someone please confirm that the software is the same? I've been on the family plan for many years.