dʒˈɑːn ˈɜːvɪn ɡɹˈɛɡ wʌz bˈɔːɹn ɪn bˈɛlɪfˌɔnt, pˌɛnsɪlvˈeɪniə, ðə ɡɹˈændsʌn ʌv ˈændɹuː ɡɹˈɛɡ ɐ jˈuː.ˈɛs. sˈɛnəɾɚ fɹʌm pˌɛnsɪlvˈeɪniə ænd ɐ kˈʌzən ʌv fjˈuːtʃɚ jˈuːniən dʒˈɛnɚɹəl dˈeɪvɪd mək mˈɜːtɹi ɡɹˈɛɡ.
John Irvin Gregg was born in Bellefonte, Pennsylvania, the grandson of Andrew Gregg (a U.S. Senator from Pennsylvania) and a cousin of future Union general David McMurtrie Gregg.