I cannot find any of them in 1881, not Alfred & Annie nor any of their children Horace, Alfred, George or Florence all born before 1881.
Possible 1889 shipping record but only two possible fits for children. One of the infants would be Frederick born 1888 and the 8 yo could be Margaret. So when did Horace, Alfred, George and Florence arrive? Or are the ages all mixed up? Or are the 6, 5 & 3 yo and the other infant children of Mr J & spouse? Neither the 45 or 34 for Mrs fits with age at death for Annie.
Parents' deaths:
Surname: BLENKARN
Given Names: Alfd Elston
Event: D = death
Father: Blenkarn Alfd Bower
Mother: Mary Ann PAGE
Age: 53
Death Place: Melb W = Melbourne West, Vic.
Year: 1903
Reg. Number: 10822
Surname: BLENKARN
Given Names: Annie
Event: D = death
Father: Peart Geo Symes
Mother: Maria Ann UNKNOWN
Age: 60
Death Place: Hawth = Hawthorn, Vic.
Year: 1910
Reg. Number: 5588
Unassisted to Victoria:
Family Name First Name Age Month Year Ship Port Fiche Page
BLENKHORN ---- CHILD WITH 6 NOV 1889 AUSTRAL B 523 015
BLENKHORN ---- CHILD WITH 5 NOV 1889 AUSTRAL B 523 015
BLENKHORN ---- CHILD WITH 3 NOV 1889 AUSTRAL B 523 015
BLENKHORN ---- CHILD WITH 8 NOV 1889 AUSTRAL B 523 015
BLENKHORN ---- INFANT WITH I NOV 1889 AUSTRAL B 523 015
BLENKHORN ---- INFANT WITH I NOV 1889 AUSTRAL B 523 015
BLENKHORN ---- MR 40 NOV 1889 AUSTRAL B 523 015
BLENKHORN ---- MRS 45 NOV 1889 AUSTRAL B 523 015
BLENKHORN ---- MRS 34 NOV 1889 AUSTRAL B 523 015
BLENKHORN
J MR 48 NOV 1889 AUSTRAL B 523 015
=====
Possible - I have nothing yet to support this
Births Dec 1860
BLENKARN John St Saviour Southwark 1d 7
Marriages Mar 1880
Blenkarn John St. Saviour 1d 61
Clack Sarah St Saviour 1d 61
Johnson Emma Elizabeth St Saviour 1d 61
Longbon George St Saviour 1d 61