Kassie was born in Cape Town. He grew up with horses and started competing in horse sports from an early age.
At the age of 19 he joined the South African Defence Force as a PF member. He was situated at the Equestrian Centre where he held the rank of Major. In 1993 Kassie represented the National Defence force in South America doing show-jumping.
After his military career Kassie became Stud Manager at Odessa Stud working alongside Lionel Cohen for 6 years. He then joined the group at Maine Chance Farms where he worked with the horses – as well as ran the agricultural side of the stud farm concerned with pasture management and forage production.