Not sure how much you have found but thought I'd do some digging:
William GALT b. 1904 to William GALT & Margaret Annie BLAIN (reg C6164). He had a brother named Albert James b. 1907, m. Elizabeth Lily CRITCHLEY 29/9/1934, d. 24/6/1941. They had a son and a daughter.
The Courier Mail, Wednesday 25 June 1941
GALT.— The Relatives and Friends of Mrs. E. L. Galt and Family, Mr. and Mrs. W. Galt (Charters Towers), Mr. and Mrs. Critchley (Charters Towers), and Mrs. C. Mundy are invited to attend the Funeral of her beloved Husband, their Father, Son, Son-in-law, and Nephew, Albert James Galt, of Roma, to move from Alex. Gow's Funeral Chapel, Petrie Bight, This (Wednesday) Morning, at 11.30 o'clock, for the Crematorium, Mount Thompson. No flowers, by request.
William GALT (snr) married Margaret Annie BLAIN in 1901 in Qld (C2251). Where did you get her mn as HOUGHTON?
Wm died in 1955, son of Hugh GALT & Mary HUTCHINSON (reg C4960). Margaret died in 1963, daughter of Peter Imrie BLAIN and Margaret GILLESPIE (C700).
William had brothers in Qld: Hugh (d. 1954 C4171), Halbert (d. 1960 B41536) and Robert Hutchinson GALT (d. 1952 B38448). They arrived together in Qld on board 'Jumna' 12 Dec 1889; William (12), Halbert (14), Hugh (15) and Robert (16). So young! No adult GALT was with them :(
Halbert married widow Helen [Ellen] Amelia EDWARD (nee REED) in 1898. Hugh married Mary CHRISTOPHER in 1909.
Robert served in WWI aged almost 43 when he enlisted, single, and iron moulder by trade:
Galt Robert Hutchinson : SERN 870/85912 : POB Kilmarnock Scotland : POE Holsworthy NSW : NOK B Galt Albert
Burials for Robert, Halbert and Ellen Amelia at online.brisbane.qld.gov.au/cemeteries/cemeteries_step2.jsp
Margaret's father Peter Imrie BLAIN died in Qld in 1925, son of Thos BLAIN & Annie GALLOWAY (C1024). Her mother died as Margaret Walker BLAIN in Windsor, Brisbane in 1948, daughter of Jas GILLESPIE and Margaret WILLISON (B16574). She was 91!
Peter (25), Margaret (26), Maggie (2) and infant M G arrived in Qld aboard 'Duke of Argyll' 11 Nov 1884.
From NLA Trove:
The Brisbane Courier, Monday 1 June 1925
HOSPITAL TRIBUTES TO PIONEERS.
TOOWOOMBA, May 31.
Two important functions took place at the Toowoomba Hospital this afternoon. The first was the unveiling of enlarged photographs of Dr. Frederick Otto Sachse (founder of the first Toowoomba Hospital in 1800) and Dr. Stephen Flood (the first medical superintendent o£ the present institution). The second function was the formal handing over of a bed, an invalid table on castors, and a chair donated by Mr. and Mrs. G. Kowitz, of Cecil Plains, in memory of the late Mr. Peter Imrie Blain, father of Mrs. Kowitz...