A few pointless little quandries:

1. What type of planet might our Earth be? What would a planet that looks like our Earth be classified as? Much of it has water, grass, trees, and stuff. The bulk isn't a Hive, a Forge, or what have you. Maybe a minor Agri-world?

2. In the Navis Nobilite, how "family" are the members of a House? Are they all genetically related, or can they absorb another bloodline in to fight inbreeding?

3. Navigator Gene is recessive, yes? Thus, both parents must have the Navigator gene, and it must be active?

4. For "important" people, is pregancy carried out? Could/would they just take an egg and sperm, and grow it in a tube, or would they have an important Navigator spend several months pregnant, and risk their lives? I'm not sure exactly what level of tech the Magos Biologis have and use.

This all has to do with a story of mine. My Navigator is expected to further an experiment she is a part of, and I assume to have a Navigator child, her mate would have to be another Navigator, rather than the Human she loves, preferably of her House, but I don't know how closely related that would make them. Also, as someone born in space, and a member of one of the Nomadic Houses, she hasn't been to planets much, but I want her love interest to take her to the surface of a world where they stopped to resupply, and I want it to be a world with a bright sun, clean air, grass, and such. Even a spaceborne girl like her should be a bit moved by the pure light, unrecycled air, and such, but I don't know what type of world, other than Agri, would have an environment like that, and if they'd stop above one of those, for food, water, and air resupply. Also, as the prototype of her father's genetic manipulation program, it becomes important to see if her genetic excellence carries into the next generation, but I don't know how closely related the othe Navigator would end up being, and if her love interest would be with her while she's pregnant, or if they would free up her time, and just grow the child in a machine?

1 - Paradis World, here people coem to relaxe and enjoy thier life… Agri we have too high population, major culling would be needed ot insure over production of food and currently well we don't really have "enough" to feed all of us so don;t think about feeding other planets…

2 - from a few hundred to many hundred thousands. Some familly have starfortress comparable to those belonging to the astartes… (spacewolf book where ragnar is a navigator honor guard).

3 - Tehcnically interfamilly mariage, but again 40k all is possible.

4- all is possible.

A problem with planetary classifications is probably that our modern-day Earth has so many different climate zones and unique environments, whereas 40k has a tendency to have worlds be "that ice planet" or "the desert world" or "the city planet"… parts of Earth could undoubtedly classify as Paradise, yet others are too polluted, too overpopulated or even just too cold or too hot. All in all, I'd probably just classify it as a standard Imperial world. A former Feudal world that has "recently" been industrialised. But of course that is debatable and it depends a lot on one's interpretation.

And interpretation is also the keyword for the other questions! The franchise does not propagate something like "a single truth" where you could point to a book and say "that's how it is" - instead, we are presented with a selection of options, "lenses through which we can view the universe" as Aaron Dembski-Bowden once metaphorically described it, which also explains why there are so many contradictions between the various sources. You can cherrypick or ignore what you like, and you can invent new things that you believe would fit. Games Workshop wants you to make this setting your own.

But if you're looking for inspiration - GW's old Inquisitor RPG had an article on the Navis Nobilite that can still be reached via the internet archive. Amongst other details, it discusses the nature of the Navigator genome as well as the organisation of a House:

http://web.archive.org/web/20071218085326/http://es.games-workshop.com/especialista/inquisitor/bestiario/fleet.html

Hope that helps. Good luck with your adventures!

I would have to assume that Navigators can produce Navigators from marriages with non-Navigators. I mean, they've been around a while, it seems safe to assume these houses wouldn't still be standing if their prospects were limited to themselves. The gene was intentionally created to give the Imperium access to faster-than-light travel, and considered basically a necessity for a working empire - why wouldn't the creators have made it dominant? Also, limited to inbreeding would not make the Navigator population easy at all to increase, and an ever-expanding Imperium needs more and more Navigators each decade. Finally, it just doesn't feel very "in theme" for Navigators to be limited in that way, not to mention that there would surely be laws against their marrying non-Navigators if they were. They'd feel more like Astropaths - bottom-class citizens enslaved to the Empire - than the elite nobles that they are if they had specific restrictions on who to marry.

And face it, most parties assume no more than a handful of NPC Navigators and only one NPC Navigator per RT vessel. You don't want to give the "playa" of the party the most limited options for sexin' up the NPCs, especially with all of them having a creepy third eye on their foreheads and various unusual defects. Not to mention, what happens when a pair develops awkward mutations…. "By the Emperor, how did you gain 450 pounds in the last two days?" "How did you drop to only 65 pounds in the same time period?" "…..you will break me if we make love." "Yeah, probably."

I'd say we are classified as a civilized world.

http://wh40k.lexicanum.com/wiki/Civilised_World#.UZ5ZjYd_4b0

A Navigator House is not what probably springs to your mind when you think of a family unit, within it would be a great many family units but it's a clan likely to contain as few as say fifty indivduals to as many as several thousand. As navigators their talent set is in high demand, and their population of professionally functioning members is going to be the determinator of their wealth and influence as a clan. That being the case whenever a pairing produces strong offspring there will likely be encouragement to keep pumping out kids.

As for the inbreeding it's no doubt and issue and happens with far too much frequency, however the houses probably intermarry or at least interbreed with great frequency. Considering the nomadic nature of their profession any time two navigators of opposite sex and breeding age with really strong/pure genes cross paths they may be likely to engage in baby making assuming they're able to negotiate a contract as to who gets paid what and who gets to keep the kid under what conditions etc.

I'm not sure at what point in their lifespans most of the breeding takes place, but my suspicion is that the majority probably occurs sometime after the Navigator begins to establish themselves professionally but before they go completely freakshow. I'm not super clear on the internal clan structure either beyond it being ruled utterly by patriarch or matriarch but my suspicion is it's alot like say the Lannisters on Game of Thrones, there's a shitton of them but only a handful hold all the power or really matter politically and all the rest both resent the hell out of those guys but only because THEY want to be in that club too..

Another thing to think about is that the Imperium has Iron Wombs used on some worlds to produce troops (Kreig). The Navigator Houses are allowed a great deal of lattitude due to their value to the Imperium. I would be very suprised if they allowed a working navigator to leave her position for a year just to have a child. I expect that exposure to the stress and warp contamination of acting as navigator for a ship is probably a great way to create monsters, if not simply killint the fetus. I know that in our group, the navigator is suprisingly free of mutation for all her skill and abilities (she has never failed a test to prevent mutation). She is being pressured to breed by her house, as they are still recovering from losses taken decades ago. She is planning to have several children via Iron Womb to allow her to continue her career while serving her house.

I can only answer #1 Earth as it is now would be concidered and Imperial World, pretty much your bog standard planet in the imperium. We arent as densely populated as a Hive, we dont have the vast farms of an Agri-World, and we dont have the giant factories of a Forge World. So it does seem that Imperial World is a good fit. Also, we have a descent level of technology (though if we were in the 40K universe it should be hire, with cities such as New York on their to becoming hives.)