Missing links

I'm currently using the graphviz noderef module for a lineage website.
It is missing some links though. If two parent nodes have a common parent node the lines to not reconnect at the common parent.

See the attached image. --- Anko Itosu and Matsumura 'Bushi' Sokon should be connected.

If I visit the node for "Anko Itosu" it is displayed correctly. It is only displayed incorrectly when two (or more) parent nodes of the current node.