These are the birth registrations and BISA children, Deirdre.....
Hannah Elizabeth Her birth in South Australia
Ann Eliza HEARD born 20 Aug 1853 at Port Adelaide
Father = William HEARD & Mother = Elizabeth MCBROOM
ref = Ade 4/209
Her birth as registered in Victoria born in 1853 in ADEL
Anne Eliza HEARD
Father = William & Mother = Elizabeth MCBROOM
Ref = 945
Robert James (1855-),Listed in BISA
Probably died in infancy. Was his death registered? Can't find it in either state...
Thomas David (1857-), Thomas David UNDERDOWN born 1857 in DUNOLLY
Father = Robert & Mother = Elizabeth MCBROOM
Ref = 11946
Joshua George, died aged 22 months in 1861 in Victoria.
Father = Robert UNDERBROOM & Mother = Elizabeth McBROOM
Ref = 3282
Was this his birth and his name registered differently? Because there is the following.....
Charles Alex UNDERDOWN born in AMHERST in 1859
Father = Robert & Mother = Elizabeth Ann BROOM
Ref = 15227
Mary Elizabeth Ann (1861-), Her birth….
Elizabeth Ann UNDERDOWN born Inglewood 1861
Father-Robert Mother-Elizabeth Ann Brown
Reg no 17652
She was also known as Mary Elizabeth Ann......
Mary Elizabeth A JENKINS died aged 82 at Carnegie in 1944 reg no 4030
Father Robert Underdown
Mother Elizth MCBROOM
Sarah Jane (1863-, As listed in BISA but can't find her birth but.....
Her marriage
Sarah Jane UNDERDOWN married David SCOTT in 1887 at EMU CK
Ref = 537
SCOTT Sarah Jane
Father Underdown Robt Mother Elizth Ann MCBROWN
Death Place EWICK 83 years 1947 Reg# 2664
Robert James Charles (1865-),Listed as Robert Charles James Alexader on mother's death certificate....
Robert Charles Alexr UNDERDOWN born at SHURST in 1866
Father = Robert & Mother = Elizabeth Ann MCBROOM
Ref = 4796
William Joshua George (1867-), As listed in BISA but can't find his birth either.....
His marriage in EMU CK in 1896 to an Eliza McKinnon.
Ref = 1797
burial at Karrata.
UNDERDOWN WILLIAM JOSHUA aged 60 years 1929
Henry Emanuel (1874-) Henry Emanuel UNDERDOWN born at STRA in 1875
Father: Robert & Mother = Elizabeth Ann MCBROOM
Ref = 5819
They didn't want to make life easy for their descendants.....

......dee