The primary purpose of creating a family is to make it easier to manage parental controls and online safety for children. You can manage who is in your family from your Xbox One console, or from any Windows 10 device.
Any adult in the family can remove another family member. Children and teens are prohibited from making this change.
When a child is removed from the family, they will be unable to use the Xbox service until they have been added to another family. See Add a new member to your family.
Adults removed from the family no longer have the ability to manage the child accounts in the family. However, they'll have full rights to their account and will be able to use home console sharing when signed in to the home console.