Many records were destroyed in a V.A. fire back in the 70’s, but if you have any of his military records (specifically discharge papers) you might be able to get to the truth. many young boys enlisted by lying about their age. My own father enlisted at 15, was discovered and booted out. He then joined the CCC (Civilian Conservation Corp) and planted trees, and when he came of re-enlisted. Your own father may have succeeded and been accepted. one of my ancestors assumed his brother’s commission in the Revolutionary Army when he was probably 13-15 years of age. Many who fought (and still fight today) are very young warriors. Good luck in your journey of discovery!🇺🇸