William Robertson Watt was born on Wednesday 11 July 1906 in Leith, Scotland.

William married Hilda Mary Bourne on Saturday 17 August 1935 in St Pauls Church, Sydney, Australia.

He had the following children from his marriage to Hilda Mary Bourne:

- Margaret Hilda Watt	born in 1937 (date suppressed) in New South Wales, Australia.
- James Alexander Watt	born in 1945 (date suppressed) in New South Wales, Australia.

Details of William's occupation are not known.