Hi there Omega
I found the following births on Victorian BDM
UNDERDOWN Robert Charles Alexr born 1866 Shurt Reg no 4796
UNDERDOWN Henry Emanuel born 1875 Stra Reg no 5819
Father: Robert Mother: Elizabeth Ann McBroom
UNDERDOWN Thomas David born 1857 Dunolly Reg no 11946
Father: Robert Mother: Elizabeth McBroom
There are several deaths in Queensland
for the children of Robert and Bredelia Underwood that you can
look up on this site www.justice.qld.gov.au although the deaths
are only recorded up until 1914.
Hope this is some help to you

Raylen