So, Genestealers are an interesting antagonist. They can put a human face on xenos infiltration. I've been planning to use them in some of my recent adventures and I've found some good fan-based rules for them.

However, I have run into a slight background problem. "Brood Brothers" are described as the literal brothers or sisters of the hybrids. In my 40k readings I've certainly come across the term before. However, what does this mean, exactly? My original interpretation was that brood brothers are the non-firstborn children of those humans infected by the genestealer's kiss and that they are biologically human but form a cult of sorts around the Genestealer Patriarch. However, some fan-made rules give these brood brothers hive mind rules that seem to conflict with the idea that they can pass cursory gene scans and infiltrate planetary governments.

So, just how human are Brood Brothers? How different do they feel from a normal human, and how hard would they be to differentiate from them?

Hi,

as far as I got it (and treat it), they genes of a brood-brother are infiltraited by that of the Genestealer-Patriach. They are not 100% human any longer.
How thorough a genetic screening is needed depends on the how thorough the infection is. At some point, the mutation is to plain obvious to be hidden.

My two cents based on what I have seen in my tabletop times.

Not sure wheher more recent changes to the fluff have altered this, but my understanding of Brood Brothers was that they were the human parents of genestealer hybrids. As they've had part of their brain absorbed by the hybrid in the gestation process, I'm not sure how "human" they are, apart from physically. As genestealer ovipositors can in theory infect both genders, I'd imagine there's probably some genetic tweaking going on with them too, if accommodations for a hybrid need to be made.

But this is all dated from the 90s, so if things have been updated a bit more recently I'd be grateful to hear.

I don't know about any changes in recent years, as I simply don't have enough "me time" to get in to reading the novels. That being said, my first 40K army was a genestealer cult as presented in White Dwarf #118. The ORIGINAL life cycle of a genestealer brood went like this:

A purestrain genestealer uses the "genestealer's kiss" to implant its genetic material into one or more host organisms. For this example, there will be a single human host. The human experiences an overwhelming desire to settle down & start a family. He or she (doesn't matter) will find a mate & choose to start their family in a location that is safe & isolated, if possible. The first child born is a first generation genestealer hybrid. These have mostly genestealer characteristics, including one (sometimes two) genestealer claw arms in addition to their humanoid ones. The hybrid's natural brood telepathy forms a bond with the parents, causing them to lovingly protect & dote on the infant monster. They can now be considered Brood Brothers & the original genestealer can be considered a Patriarch. A brood brother couple can only ever sire one hybrid, with any additional children being "normal" humans, though brood brothers themselves. The first generation hybrid will use its ovipositor to infect another human. the cycle repeats & a second generation hybrid is born. These are a bit more human, but still monsterous & sporting a claw arm along with their human ones. Second gens can also use huma technology & weapons, though not with any real skill. The second generation hybrid infects a human & the cycle repeats, producind a third generation hybrid. Third gen hybrids are much more human, having a human body shape. They are born with a claw arm about 50% of the time. They are still obviously inhuman, but could get by if in fully concealing clothing or darkness. About half of third gens are born without an ovipositor & are thus infertile. The fluff did state, however, that they could infect a host by injecting their blood or through normal sexual means. The cycle repeats & the first fourth generation hybrid is born. These are almost 100% human in appearance, being hairless with a heavy brow. The first fourth gen hybrid born is called the magus & is the figurehead for the cult. He is always a powerful psyker, as are most fourth gens that come after him. The fouth gen must reproduce as a human would, giving birth to a purestrain genestealer. By the time these are born, the cult will be quite large & powerful.

So... all Brood Brothers are the normal human relatives of the brood. They are completely & suicidally devoted to the protection of their xenos kin. In the TT rules, they were represented by IG troopers with Haterd and a higher leadership (I think). I could go on & on about cult strategy & such, but this post is already long & it would be off topic.

I made a nice fanplement a few years back, this was before the Inquisitors Handbook was published and Black Library ending the line.
It might not be completely correct but it should serve as a nice source of inspiration.

http://darkreign40k.com/drjoomla/index.php/component/docman/doc_download/69-genestealer-cults

Thanks for all your help. This has been very useful.

Santiago said:

Ha, you're a bit late. That file already safely resides in my 40k folder. It's a good work and I'm trying to use that as a base for what I'm working on. Well done!

Santiago said:

I just got around to looking at this link. Quality work, thank you!