Artificial womb technology is a common luxury in society by those who can afford its exorbitant costs. Wealthy families and noble houses use it as an extension of their own power. However, artificial wombs are not used to make childbirth any safer. Instead, it is used as a way to grow and replace workers. The struggle of delivering a child after carrying it for twelve months is considered a superior way to have children and is regarded as a mark of prestige. These children are seen as the true nobility, while vat grown children are considered part of an extended family created to serve the main branch.
Sperm and egg samples are taken from members of that specific bloodline and fertilized. Genetic heredity is not documented, as it is irrelevant so long as the bloodline to the house is preserved. Each individual is born with a genetic physical marker, which marks them as vat-born. These individuals are born completely similar to regular people, with all faculties intact. However, they are infertile, preventing them from spreading their genetic material. They are raised separately from true born and trained to take on the essential but under-valued roles of a house. These are the soldiers, guards, house servants, and other positions required to keep the house running but are undesirable or present too much risk, freeing the true born to take on more valued roles.
It won't take too many generations of vat born to realize that they actually have the ability to overthrow their true born relatives, as having access to weapons and knowledge of inside house business grants them a unique position of power. I need this setup to work long term as a functional system, without any violent revolts from the lower classes. How can I make this stable and prevent vat-born from ruling over their trueborn cousins?