Kammala jumla mai zuwa: John Hepburn shi ne ɗan na biyu na George Hepburn na Athelstaneford, kusa da garin Haddington da matarsa Helen Hepburn, 'yar Adam Hepburn na Smeaton. Wataƙila ya yi karatu a St Andrews a 1615, sannan ya yi tafiya zuwa Faransa tare da abokinsa, Robert Monro ziyartar Paris da Poitiers. Hepburn na ɗaya daga cikin dubban 'yan Scots da suka yi aiki a cikin Yakin Shekaru talatin. A cikin 1620 Sir Andrew Gray ya fara tara sojoji don tallafawa Sarauniya Elizabeth na Bohemia, kuma ya kafa sansaninsa a kan dukiyar iyalin Hepburn a Monkrig. John ya shiga sojojin Gray, ya bar Scotland a watan Mayu na 1620, kuma daga baya ya umurci wani kamfani na pikes wanda ya yi aiki a matsayin mai tsaron sirri ga Sarkin Bohemia da aka kora. Bayan da
Rashin nasara a White Mountain sojojin Gray sun haɗu tare da sojojin Count Ernst Mansfeldt, kuma a 1622 Hepburn ya rike mukamin kyaftin. Ya yi aiki a lokacin yakin Bergen op Zoom a watan Yuli da Fleurus a watan Agusta 1622. Bayan da aka rushe sojojin Mansfeld a 1623 ne Hepburn da sojojinsa suka shiga aikin Sweden.