The MilBoys were just morphs for PT-Vicky and PS-Vicky. They had their own cr2's as the 2nd gen DAZ meshes had no injection channels, but they used the same object files as the MilGirls.

I remember they were available either standalone or as a MilGirls "upgrade", so they came as two different installers.

Matt and Maddie and Luke and Laura were also available as "upgrade" installers, so you could get them cheaper if you already bought the MilGirls or MilBoys.

MilGirls = PT-Vicky and PS-Vicky.

MilBoys = PT-Boy and PS-Boy.   

Young Teens = Luke, Laura and PT-Luke as well as PT-Laura who could wear PT-Vicky and PT-Boy clothes.

Preschoolers= Matt, Maddie and PS-Matt as well as PS-Maddie who could wear PS-Vicky and PS-Boy clothing.

MilGirls and MilBoys are 2nd generation figures so they are not compatible with the 3rd generation Young teens and Preschoolers.