"..I have the BDM for Andrew Morrison and Harriett Middleton but not Robert Middleton."
Can you clarify this please....you have the certificates...or you have located the events in the QLD BDM Index?
On the "Jumna"
MIDDLETON Robert 45y, Harriett 45Y, Robert 24y, Maggie 22y, Alice 19y, Harriet 17y, Annie 15y
QLD BDM marriages
1889 B13467 MIDDLETON  Margaret marr. GRAHAM James 
1892 B16009 MIDDLETON  Harriet    marr. McDOWELL Thomas
1904 C738    MIDDLETON   Annie      marr. THOMPSON Edward
1920 B26330 MIDDLETON Alice        marr.  MADDEN William  
QLD BDM death
1931 B15846 GRAHAM Margaret Jane parents MIDDLETON Robert / MORRISON Harriett Morrison 
1957 B21910 THOMPSON Annie         parents MIDDLETON Robert / MORRISON Harriett Morrison 
1942 B55357 MADDEN Alice              parents MIDDLETON Robert / MORRISON Harriett Morrison 
Telegraph 18 Nov 1911 p6
https://trove.nla.gov.au/newspaper/article/176315518?....death of Harriett THOMPSON nee MIDDLETON.......
Brisbane Courier 8 Jul 1919 p6
https://trove.nla.gov.au/newspaper/article/20372321?....funeral notice Robert MIDDLETON... (names of family)