After September 1942, the only volunteers were under 18 or over 38. Everyone else had to pass through the local draft board. The reason is that early in the war too many people who had critical skills (farmers, machinists, etc.) were volunteering.
Right, but if he volunteered at the draft board then he would bypass the exemption for fathers. Alternately if his kids were born after the war started the exemption did not apply.