A family diagram is a visual representation of the relationships between members of a family. It is often used to show the structure of a family, including the names and ages of each member, as well as their connections to one another. The term 'family diagram' can also refer to a tree-like structure that shows the ancestry of a family, with each branch representing a different generation. The term 'tree' is often used to describe this type of diagram, as it resembles a tree with its branches and roots.