👉 In mathematics, a fratrie is a group of four or more people who are related by bloodline. Specifically, fratries are defined as groups that consist of two or more individuals with a common ancestor from their family tree. For example, in the family tree of the British royal family, there could be a fratrie consisting of members such as Queen Elizabeth II's children and grandchildren, who share a common maternal line. Similarly, in the family tree of the American Kennel Club