Mervyn Johns was born in Pembroke, Wales on 18th February, 1899 and initially trained to become dentist however he met Australian concert pianist Alys Steele who he married in 1920 and who encouraged him in his ambitions to become an actor. The two had a daughter, Glynis, who later became a famous actress (appearing memorably in Walt Disney's 1964 production of Mary Poppins).