[quote=@Letter Bee]
<Snipped quote by AndyC>

How old should a 'Plucky Kid' be?
[/quote]

If they're actually fighting, I think about 16 to 18 is the absolute youngest most respectable forces would let onto the battlefield. The hero of the first three novels, Grayson Carlyle, was about 20 when he first saw combat, and he was considered exceptionally young for a Mechwarrior. While the setting has its darker moments, it doesn't really veer into full-blown child soldier levels of dark.

If you want a support or 'mascot' character running around in the HQ, they can be proper kids; most merc companies that don't have a permanent land hold have to bring their families and civilian contingent with them (though usually in a separate ship).