I know of four Henry Raeburn Browns.
1. Born about 1806/7 in Edinburgh, master tailor, married Helen Clyde, died 29 March 1852 in Edinburgh.
2. Grandson of No1 by his son Sir William Slater Brown, born 1869 in Edinburgh, died unmarried in 1947 in Edinburgh.
3. Grandson of No1 by his son Henry Brown born 1879 in Edinburgh, married Annie Baillie Phillips, killed in Palestine 1917
4. Born in Edinburgh 1917, probably the one who married Joan Day in Edinburgh in 1947, no further information
Henry Brown, son of No 1 and father of No 3, may or may not have used the middle name Raeburn, but I have yet to come across a documentary record in which the middle name occurs.
Can you give me more information about your five Henry Raeburn Browns?
Forfarian, as far as I can tell & have been able to document, Slater as a Christian/middle name was first given to Sir William, no-one else in his immediate family went by Slater until his & Margaret Dod's third son, William Slater, surname Brown, born 1875 in Endinburgh.
William had 3 brothers, eldest Henry Raeburn Brown, born 1869, died 1947 (your No. 2); George Dods Brown, a councillor, born 1872, died 1942 & Robert Dods Brown, born around 1879, death unknown. He also had 2 sisters, Margaret Ann Brown, born 1866 & Willemina Brown, born about 1876.
William Slater Brown married Agnes Euphemia McArthy in 1911 & they had 3 sons. Eldest David Maitland Slater Brown, born 1914 & mentioned in No 2. Henry Raeburn Brown's will as he died childless; middle son Henry Raeburn Slater Brown, born Edinburgh 1917 (your No. 4), married Joan Day nee Barker (born 1918, Rhodesia) in 1945; youngest son Alexander McArthy Slater Brown, born 1921 & KIA Hong Kong in 1942. All WWII/MOD records for David, Henry & Alexander had Slater as a middle name & Brown as surname.
Henry & Joan both returned to Rhodesia post WWII, took up service land, started a family & died there in 1978 & 2007 respectively. It was at this stage, in Rhodesia, that Slater (Christian name) became Slater-Brown (surname) in the next generation of documentation & their eldest son (my husband) was born Raeburn Graham Slater-Brown in Rhodesia in 1950.
Hope this helps clear up some of your questions? Though it opens up new questions for me regarding the Henry Raeburn who died in Gaza as I haven't made that connection as yet though I came across various dox whilst searching....