It has become tangled and merry chase indeed.

The line of thinking I am pursuing goes this way.
It is enormously speculative, but theories have to be explored before they can be discarded.
In Jan 1920, Robert Edward SEALE married Marjorie Gertrude WILKINS. His age is 31 (born about 1889)
The groom’s father is listed as Robert
Richardson SEALE
Was the word
Richardson a misprint? Because Reply 183 this thread shows one Robert Edward SEALE (born 1842) was a brother of Walter Earle SEALE and he had married Sabinan MADARU in 1878 with Colonel SEALE as witness.
Robert Edward SEALE, the groom marrying WILKINS may or may not have seen service in ww1.
He may or may not have been raised by Walter Earle SEALE and travelled with Colin and tutor around the world.
He knew enough about Walter and Kathleen SEALE to have some details of Walter’s work and Kathleen’s correct maiden name.
By 1922 he was using the name Robert STEVENS in NZ and in 1923 in Gosford NSW where he worked with a possible associate from his homeland, HAYNE for a while. He learnt enough about Gosford to fabricate it as his birthplace.
Robert STEVENS moved about Australia until his marriage in 1941 QLD to a young woman, our OP’s mother.
Marjorie Gertrude WILKINS, the bride of the 1920 marriage, was born 1902. Her father died in 1905 and mother remarried twice afterwards, the last marriage being to Harold William MAJOR. The mother, Winifred (nee ALMOND died in 1959)
In 1962, 64,65 there are electoral roll sightings for Marjorie SEALE, with Harold W. MAJOR and another woman in Surrey, UK. We are fairly certain the younger woman was her daughter.
There are shipping passenger sightings for Marjorie and others back and forth between UK and India which give a birthdate for the daughter as 1929.
The younger woman mentioned in sightings, in 2007 wrote to an online circus forum about her mother , Marjorie SEALE, who had run away to join the circus when young. It is stated “She may have taken on another name because she ran away to join the circus”
http://www.circushistory.org/Query/Query05a.htm Marjorie SEALE died in 1975 and is buried in England.
Overall, the line of thinking is there was a short marriage for Robert STEVENS where his very young wife left for a circus life and, in order to make a new start, Robert changed his name to STEVENS and left for NZ.
In case he had formed a bigamous marriage with OP’s mum, he composed a new life story for himself as cover.
Sue