Editing Setting:Navigator: The Masquerade (section)

== Navigator Bloodlines ==
The informed elite of the Imperium believe the Navigators possess a gene which is responsible for the manifestation of their abilities, and that this gene is recessive.  That to produce a new navigator, two navigators are required.

This is false.  As it so happens, if two navigators were to copulate, the result... would hopefully not live long, although would certainly need a bolter round to put down.

Navigators must reproduce with normal humans to maintain the humanity of their species.  As a result, each navigator has only one Navigator parent, and can trace their bloodline back to one of the original thirteen Navigators to survive the birth of Slaanesh and the opening of the Eye of Terror. 

Both a human mother and a navigator mother can carry a navigator child, but navigators born to a human mother will be born so starved for warp energy that they will frenzy at birth and must be warp bonded to force the daemon soul to give up control.