So, I've started on the SA acrchives - here's one possible hit DEPOT TAB
SOURCE MHG
TYPE LEER
SYSTEM 01
REFERENCE 7659/1964
PART 1
DESCRIPTION YOUNG, MARGUERITE ELIZABETH FLORENCE. BORN WEEDON.
STARTING 19640000
ENDING 19640000
REMARKS SURVIVING SPOUSE DOUGLAS ARTHUR YOUNG.

And this one

DEPOT TAB
SOURCE MHG
TYPE LEER
SYSTEM 01
REFERENCE 6472/74
PART 1
DESCRIPTION YOUNG, DOUGLAS ARTHUR.
STARTING 19740000
ENDING 19740000
REMARKS PREDECEASED SPOUSE MARGUERITE ELIZABETH FLORENCE YOUNG. SURVIVING
SPOUSE ANNIE YOUNG (BORN MARAIS FORMERLY VENTER).

If that is them (and I can't see any other possibilities), then Margaret (or Margarita) died in 1964, and Arthur remarried, and died in 1974. There're two ways to get those files - place an order through the EGGSA, or head to the Family History centre in Parktown. The estate files will have childrens names, and often parents names.