My grandparents were in their 40's, too old to fight and anyway both my grandfathers worked in essential industries, one in a steel mill and the other as a farmer. Their wives stayed home with the kids.
My dad joined the Army Air Corps in 1944 as soon as he turned 17. He was trained as a medic and ambulance driver but was never near the front lines. He served for a total of six years, getting out in 1947 and going back in for Korea. He made sergeant, and was even a drill sergeant for a while, which is impossible for me to imagine. My mother yes, she was perfect for that job, but not my dad. My mom was still in school during the war, graduating in 1950. Both of her brothers saw action overseas though.