Note: On the birth registration of Malcolm Charles, John has entered Sarah's age as 21 which means that she was born in 1871. Mind you he also put their wedding year as 1888 when it was 1889 according to the Marriage Certificate (and her age in Aug 1889 was 20)!
Note: Searched NSW BMD from 1880 - 1892 for these parents and no children recorded.
There is an Olive Ruby born 26/11/1896 to a Sarah Ann and a John McDonald, in the NZ register 1897/00743 BUT this would mean that Kenneth Neil who came after was born premature but still lived, as his date of birth was 15 April 1897.