Toying with my script from the previous post... Not limiting the number of generations, and processing it with neato instead of dot (still from Graphviz) gives this cool diagram... I haven't tried removing overlaps. I also have some changes to allow including siblings (the diagram below includes only direct ancestors). ...
My dad spent a lot of time putting together a family database, currently containing about 12000 people covering both my parents ancestors as well as tracking forward to contain a lot of living descendants. Unfortunately, since he started this over 16-17 years ago it's been managed as a custom dBase III+ ...