Graphviz is great if you don't mind automatic placement and routeing - here's one I put together a few years ago.
https://tekeli.li/atlantis/relationships.png
However, tweaking locations of elements is a complete pain. The two alternatives I've found are plain old inkscape (very hard work) and the diagram editor dia, which I'm using for Pendragon family trees:
https://discussions.shutupandsitdown...6a7767a79a.png
In that it's possible to attach the end of a line to an object, so that when you drag the object the line moves with it.
I've also got some basic perl code for turning a series of nodes and connections into a dia file, with the attachments already in place. That was what I used for
https://tekeli.li/wives-and-sweethearts/botein/
though the output scaling wasn't ideal.