I wanted to create one of these for a story, but I don't know what they are called. I don't think these types of ... whatever... are 'trees,' due to their multiple starting points.
I don't know the proper stack exchange to ask this on, or the tags that go with it, because I don't know what this even is.
To explain why this is important to me:
I intend on creating a similar graph to help organize. In my concept, there is a humanoid race with cities hidden in caves and underwater. Each city is ruled over by one of the original immortal alien beings that came to earth, which are called High Keepers. They each have an immortal human agent, called an Old One, and it is common for them to produce hybrid children together. For example:
City - Liggishi (located in a hidden African grotto)
High Keeper - Euuttav (considered female)
Corresponding Old One - Askrlif (male)
Hybrid child - Dynglao (female)
I wanted to form a similar chart for the purpose of listing the cities, High Keepers, Old Ones, and hybrids all at once - and ensure that I didn't confuse myself by simply listing them like I did above here.