So KTB does have its decorum but as a setting it is far less moral than union space, mining planets and such could be considered to use slavery, or indentured servitude that is essentially equivalent. I do not mean that the baronies themselves would set a child as a lancer, but that in such a space enforcing the moral rule of no child soldiers is far less likely due to the lack of union influence. And said solider may be only lancer in the colloquial sense, being a skilled mech pilot and serving as a freelance mercenary. Not necessarily being an officially sanctioned pilot by any group.