The following is a Plus Edition article, written by and copyright by Dick Eastman.
Almost all genealogists are familiar with pedigree charts. These are basic charts for recording parents, grandparents, and earlier generations for an individual. Pedigree charts are used to show bloodlines and are limited to displaying only ancestors. Pedigree charts do not display siblings, cousins, aunts, uncles or other extended relatives. Here is an example of a pedigree chart:
Pedigree charts have long been a standard tool used by genealogists and others. They are easy to understand and clearly display a lot of information in a small amount of space. However, pedigree charts are limited in what they can display, normally showing only the name of each individual and the places and dates of birth, marriage, and death. They do not show relationships of siblings, cousins, aunts, uncles, or other extended relatives. They also do not display the dynamics of a family over multiple generations.
Medical professionals also have a need to show family relationships in order to understand inherited medical conditions. The medical community often needs to collect and display information about patterns of mental and physical illnesses such as depression, bipolar disorder, cancer, substance abuse, and other diseases that seem to run in families. Pedigree charts are ineffective for such uses.