Again, from my armchair online index searching I cannot find ANY children for our OP’s couple who married in May 1855 at Tea Tree Gully.
Perhaps Martin could explain the source he used to confirm the four names.
https://www.genealogysa.org.au/resources/online-databases.html There’s Maria HAINES marrying in 1854, Adelaide district, husband as William HARMER and there’s SA births for two likely children to that couple:
1857, Mary Ann, father as William HARMER, mother as Maria HAINES, Highercombe District
1858, Ephraim, father as William HARMER, mother as Maria HAINES, Highercombe District
Possibly an infant death, 1858 Mary Ann HARMER, with father as William HARMER, Highercombe District.
I wonder if there's been some confusion over time in handwritten family documents perhaps someone a couple of generations ago thought that Ephraim and Mary Ann HAINES were the parents rather than William and Maria HARMER.
There’s a Mary Ann HAINES marrying in 1859, Highercombe District, husband as John HARMER.
There’s a Mary Ann HARMER marrying in 1855, Adelaide District, husband as Ephraim HAINES.
From Trove
http://trove.nla.gov.au/ (free to search)
http://trove.nla.gov.au/newspaper/article/49829879 . Register 28 Oct 1859
Mary Ann, youngest daughter of William HAINES, gardener of TeatreeGully, John, youngest son of Edward HARMER.
http://trove.nla.gov.au/newspaper/article/48552537 Register 19 June 1854
Highercombe District Council
William Haines … appointed public poundkeeper of yards lately erected on Section 5500, Teatree Gully,
http://trove.nla.gov.au/newspaper/article/207018769 Adelaide Times 20 Oct 1854
Impounded at the Public Pound, Tea-tree Gully
….. William Haines, jun., Poundkeeper.
“jun.,” would be usual abbreviation for “Junior”, indicating that there’s also a William Haines “SENIOR” present at Tea-tree Gully at that time.
http://trove.nla.gov.au/newspaper/article/207072978 Adelaide Times 24 Aug 1855
Meeting in the Highercombe District
…Mr William Haines, sen., seconded the proposition.
“sen.,” would be the usual abbreviation for “Senior”
JM