He was ordained priest on March 13, 1937, was vicar in Berg en Terblijt from September 1937, vicar in the parish of Sts . Nikolaas & Barbara in Valkenburg from May 1939, parish priest in Rothem near Maastricht from September 1955, retired from February 1964, first in Overbunde, then in Valkenburg. Arrested on February 02, 1942. Via prison in Maastricht, concentration camps Amersfoort, Oranienburg and Dachau, liberated there on May 20, 1945. 
Cammaert wrote : Vicar G.H. Hennekens copied in Valkenburg sermons of Von Galen , bishop of Münster, and his pastoral letters. He quoted them again and again during his Sunday sermons and did not hide his anti-German feelings. In the course of 1941 he came through officer H.A. van Roy of the municipal police of Valkenburg in contact with the group Smit, who declared themselves willing to take care of the distribution of the stencils. The Smit group was a circle of members of the resistance around former military officer J.L. Smit in Heerlen. They focused on collecting weapons and ammunition, the distribution (and sale) of the first illegal magazines such as Vrij Nederland, as well as the sale of photographs of the royal family. With the money that was earned from selling these photos, the costs were combated.
Because of his popularity Von Galen was not arrested but placed under house arrest. Vicar Hennekens might have hoped that too, but he was arrested on February 2, 1942. He was brought to the concentration camp in Dachau near Munich
By endangering himself publicly, he resisted to the nazi’s in a way that many did not understand. But he has given a signal and encouraged others to resist. In September 1955 he was appointed pastor in Rothem. Retired early due to health problems due to his camp period. Moved back to Valkenburg. Buried: St. Agnes, Bunde
See the article by Hub Hennekens jr. about his godfather in the book Valkenburg 75 jaar bevrijd , p.35.