He was the Laird of the Holm of Dalquairn & Glencrosh.
Robert of Holm married Mary, daughter of James Goldie Of Stonehouse and Morbrack, on 27th September 1825. She was A great-great-grand—daughter of Bonnie Annie Laurie. He died in 1858 and left issue:- John who succeeded to Holm. James died unmarried. Anne married a Mr. J. Barber of Tererran. Mary married her cousin, John McMillan of Barlae and Dalshangan. Margaret married a Captain Donnan. Jane married Robert Hamilton, F.R.C.S. of Magherbury, Portrush. Source: Clan Macmillan by Somerled Macmillan
1841 census, Glencrosh, Glencairn: Robert Mcmillan 45 Mary Mcmillan 45 Mary Mcmillan 11 Jane Mcmillan 9 John Mcmillan 8 James Mcmillan 7 Mrs. Jane Dickson 45 Jane Mccaw 20 Mary Steel 20 Janet Edgar 20
1851 census, Glencrosh, Glencairn: Robert Mcmillan 57, Farmer Of 13500 Acres Em 19 Lab Mary Mcmillan 57 Mary Mcmillan 27 Jane Mcmillan 18 & 11 Months John Mcmillan 18 James Mcmillan 16 John Mcmillan 55 Margt Miller 24 Lillias Mc Kay 22 Janet Kerr 32 David Paterson 17 John Biggar 14
The following were living at the Holm of Dalquhairn in 1851: James Milligan Head Married 40 M Farmer of 120 acres arable, 2000 acres
Mountain pasture employing 8 men & 3 women Dumfries, Kirkconnel Jean Milligan Wife Married 36 F Ayr, New Cumnock Agnes Humphry Servant Unmarried 26 F House Servant Ireland Margaret Stewart Servant Unmarried 15 F House Servant Dumfries, Closeburn Robert Barbour Servant Unmarried 31 M Farm Servant Kirkcudbright, Dalry Gilbert Ferguson Servant Unmarried 20 M Shepherd Ayr, Straiton Agnes Hyslop Servant Unmarried 14 F House Servant Kirkcudbright, Dalry James Cunningham Labourer Unmarried 23 M Ag. Labourer Ireland John Brown Labourer Unmarried 20 M Ag. Labourer Ireland
Gravestone inscription at Carsphairn Parish church: Robert McMillan of Holm Who died at Glensrosh 3rd December 1858 Aged 65 years. Also of Mary Goldie Relict of the above who died at Upper Kirkudbright Glencairn 6th Nov 1870 aged 77 years. Also of the Following members of their family Margaret (Mrs Donnan) Died 3rd Dec 1863 aged 35 years Buried in Belfast. Mary (Mrs John MacMillan) Died 27th Dec 1885 Aged 56 years Buried in Glencairn. Anne (Mrs Barber of Teberban) Died 17th Feb 1889 Aged 62 years Buried in Glencairn. James Died 7th May 1896 Aged 62 years Buried in Glencairn Jane, wife of Robert Hamilton of Magherabucy Portrush, Died 5th Sept 1897 aged 73 years Buried at Portrush.