Susan, I am a Robert Whitelaw in Sydney descended from Robert Whitelaw (1847- 1923)who was George Whitelaw (1851- 1940)surviving elder brother. George was your Robert leslie Whitelaw's father.
I have a reasonably good family tree going back to Airdrie and the village of Symington to an earlier Robert Whitelaw (1731- 1811)- your John Whitelaw's grandfather. I have photos of the graves at Symington Kirk.
When you get into it you will find the family had a Robert, John and George as favoured names- with grandfathers, fathers, sons and nephews all alive at the same time wuith the same name. They also re-use a name within the same generation if an earlier child died.
I also have copies of your George (Bowman) Whitelaw's wedding certificate from Victoria; his inquest statements following the suicide of his eldest brother (John Whitelaw 1845- 1876); and his will- alomng with bits and pieces from your Robert leslie Whitelaw's brother and sisters, which I am happy to pass copies on.
For my part, I have always been curious to have some insight into the apparent breakup of the family in Melbourne around 1876- the brothers moving to New Zealand and Sydney while the mother and sisters remained seemingly disconnected in Melbourne.