It's simply not possible to share iCloud+ without adding them to your family. This brings financial and privacy concerns. The organiser's payment method can be used by family members for App Store purchases. You can stop this by turning off purchase sharing, but then family members will no longer have access to each other's purchased apps, subscriptions etc. Secondly, they can also see the list of your devices (with half masked serial numbers ). Lastly, only the organiser can remove you from the family sharing. There's a tedious process to do it without them which involves contacting apple support. Learnt it the hard way from my ex.