There's a 25 year gap between the ages of Gordon Jones and Carol Nugent who play brother and sister in this film. However, they could just be the same father's children from different wives or Gordon Jones' character might be intended to be younger than his real age. It is even possible that they are the children from the same parents and that their age is accurate. If his parents had him at 19, it would be possible to have his sister at 44.