It looks possible that living in No.1 and 3, next to Robert and family in the 1851 Census could be Robert Laurie's brothers:
LAURIE Margaret, daughter of William Laurie, 4, born Girthon Kbt
LAURIE William, head of household, MINER, 40, born Girthon Kbt
LAURIE William, son of William Laurie, 7, born Girthon Kbt
LAURIE Catherine, daughter of William Laurie, 6, born Girthon Kbt
LAURIE David, son of William Laurie, 2, born Girthon Kbt
LAURIE Grace, daughter of William Laurie, 1, born Girthon Kbt
LAURIE John, son of William Laurie, 9, born Dalry Ayrshire
LAURIE Margaret, wife of William Laurie , 30, born Kirkcudbright K
Address: 3 Swan Street, Village of Gatehouse(866) Parish: Girthon
LAURIE Agnes, wife of John Laurie, 36, born Balmaclellan Kb
LAURIE Agnes, daughter of John Laurie, 1, born Girthon Kbt
LAURIE Edward, son of John Laurie, 5, born Girthon Kbt
LAURIE John, head of household, LABOURER general, 41, born Girthon Kbt
LAURIE Robert, son of John Laurie, 7, born Girthon Kbt
LAURIE William, son of John Laurie, 13, born Girthon Kbt
Address: 1 Swan Street, Village of Gatehouse(866) Parish: Girthon
I think that Gadget's find on IGI for Robert's parents looks good (although as a submitted entry, the christening date does seem slightly out):
There are the children showing on IGI for a John LAURIE and Catherine PORTER:
1. WILLIAM LAURIE Birth: 1811 Girthon, Kirkcudbright, Scotland
2. NANCY THORBURN LAURIE Birth: 27 MAY 1822 Girthon, Kirkcudbright, Scotland
3. Robert Laurie Birth: 09 JUN 1808 Gatehouse Of Fleet, Kirkcudbright, Scotland
4. CATHARINE LAURIE hristening: 22 SEP 1828 Girthon, Kirkcudbright, Scotland
5. ANNE LAURIE Christening: 16 APR 1820 Girthon, Kirkcudbright, Scotland
6. JEAN LOUREY Christening: 28 MAY 1804 Girthon, Kirkcudbright, Scotland
The girls' entries are all actual extracts, the boys' are submitted entries (may be something to do with only girls' records being loaded onto IGI for this period perhaps?).
There is an actual extract for what looks like parents' marriage:
JOHN LOWRIE Marriages: Spouse: CATHARINE
Marriage: AUG 1803 Kirkcudbright, Kirkcudbright, Scotland
There is also a submitted entry for this John's death on IGI, perhaps something to follow up to see where the precise date comes from:
John Laurie Death: 20 FEB 1832
Regards.
Monica