Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hi there!
You actually did it correctly. However, turning off the renewal doesn't mean that your subscription has now ended. You still have 5 days left before it is cancelled automatically and by then that's the only time the Microsoft 365 Family will appear or be shared to your account.
So long as you are already invited, just accept it or check your account at https://account.microsoft.com/services page once your current subscription expires and that will allow you to use the benefit of the family plan.