Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
If you have a Microsoft 365 Personal subscription, that entitles you to install and use Office on up to 5 devices that you log into and use at the same time.
If you need to install and use the Office apps on more that 10 devices at the same time, then you would need to purchase the Microsoft 365 Family subscription, and use separate Microsoft accounts for each of you, then the person who owns the Microsoft 365 Family subscription can share the subscription with the other family member, each of you can then install Office on up to 5 devices that you log into and use at the same time, that is a total of 10 devices.
To switch from the Microsoft 365 Personal subscription to the Family subscription is a complete new subscription, then the remaining time left on the Personal subscription would be converted to the Family subscription at a pro-rata basis, that is explained in the 'Switch to a version of Microsoft 365 that has more features' section on this link.