Drukhari, like normal Eldar, suffer from low birthrate and fertility problems (the rampant violence and drug use in Commorragh doesn't help).
Trueborn exist in all strata of DE society, I'd say, and they are always viewed as 'better,' although not enough to be of a higher social class. (A vat grown Drukhari in the Kabal of the Black Rose doesn't give a flying fanny about trueborn scum that don't merit a position in a kabal.)
Families aren't a big thing in Commorragh: a child isn't just a drain on your resources, they're a threat. Unless you can use them to increase your own effectiveness, it doesn't benefit you to have a spouse or children. (Most DE families are going to be in the same business or trade, functioning like a minor mafia family in that regard, or like a kabal in miniature.)
The fact that the poorest members of DE society have so little motivation to procreate also helps explain the low birth rate; there's no benefit in doing so, so if the Kabals want exploitable shock troops, they can pay the dosh to grow them, or so the typical Commorrite thinking probably goes.
Just my thoughts.