Robertson Cousins

HI I AM TRYING TO LOCATE INFORMATION ON MY COUSINS WHO I HAVE LOST CONTACT WITH SINCE THE 1970'S IN ADELAIDE
THEIR NAMES ARE ( PARENTS )JIMMY WILLIAM,& JOY ROBERTSON THEY HAD A SON RICKY WHO WAS A BABY IN NAPPIES AT THE TIME. SINCE THEN THEY HAD THREE GIRLS NAMED TRUDY, LINDA AND SAMANTHA. I HAVE HEARD THEY COULD HAVE MOVED TO QUEENSLAND.I BELIEVE JIMMY HAD PASSED AWAY AND WAS CREMATED , POSSIBLY NEAR BRISBANE THEY LIVED AT MAKAY, CHARTERS TOWERS AT ONE TIME I WOULD LIKE TO GET IN TOUCH WITH JIMMY'S CHILDREN OR ANY ONE RELATED TO THE FAMILY
JIMMY'S FATHER WAS LEWIS WILLIAM ( KNOWN AS BILL )ROBERTSON JIMMY HAD TWO SISTERS AND A BROTHER ALL DECEASED
HOPE SOMEONE CAN HELP THANK YOU