Following the family from 1851 to 1891 (just for reference)
The sources of these transcriptions is a mixture from Ancestry & Find My Past and as always, years and places of birth vary so must only be used as a guide.
1851 Census (transcription), Living at Clyde Bank Cottage, Yoker, Renfrewshire
Charles Duncan, Head, 51, Superintendant Carpenter of Clyde Trustees Works, born c1800, Kintyre, Argyllshire
Barbara Duncan, Wife, 49, born c1802, Kelso, Ayrshire (Roxburghshire)
Isabella Duncan, Daughter, 28, born c1823, Greenock, Renfrewshire,
Elizabeth Duncan, Daughter, 26, Dressmaker, born c1825, Glasgow, Lanarkshire
Janet Duncan, Daughter , 24, Dressmaker, born c1827, Glasgow, Lanarkshire
Robert Duncan, Son, age 20, Journeyman Engineer, born c1831, Glasgow, Lanarkshire
James Duncan, Son, age 18, Engineer’s Apprentice, born c1833, Glasgow, Lanarkshire
Charles Duncan, Son, age 13, Scholar, born c1838, Glasgow, Lanarkshire
John Duncan, Son, age 10, Scholar, born c1841, Glasgow, Lanarkshire
Anne Duncan, Daughter , age 8, Scholar, born c1843, Renfrewshire
Charles Angus, age 1, Nephew, born c1850, Renfrewshire
1861 Census (transcription), Living at Clyde Bank Cottage, Renfrew, Renfrewshire
Charles Duncan, Head, 61, Manager, Clyde Trustees Works, born c1800, Campbeltown, Argyllshire
Barbara Duncan, Wife, 58, born c1803, Kelso, Roxburghshire
Robert Duncan, Son, age 30, Ship Builder, born c1831, Glasgow, Lanarkshire
Barbara Duncan, Daughter, age 24, born c1837, Glasgow, Lanarkshire
Anne D. Duncan, Daughter, age 18, born c1843, Clydebank, Renfrewshire
John Duncan, Son, age 20, Engine Smith born c1841, Clydebank, Renfrewshire
Charles A. D. Lockerbie, age 11, Grandson born c1850, Clydebank, Renfrewshire
(Charles Angus Lockerbie, son of Andrew Lockerbie & Isabella Duncan, born 1st Jan 1850, Renfrew)
1871 Census (transcription), Living at Clyde Bank Cottage, Renfrew, Renfrewshire
Charles Duncan, Head, 71, Manager, Ship Building ‘Gard’ born c1800, Campbeltown, Argyllshire
Barbara Duncan, Wife, 70, born c1801, Kelso, Roxburghshire
Barbara Duncan, Daughter, age 36, born c1835, Renfrew, Renfrewshire
Anne Duncan, Daughter, age 28, born c1845, Renfrew, Renfrewshire
Mary Duncan, Grand Daughter, age 5, born c1866, Renfrew, Renfrewshire
(Mary Woodrow Duncan, daughter of Robert Duncan & Martha Kirkham Lees, born 10th February 1866, Govan, Lanarkshire)
1881 Census (transcription), Living at Clyde Bank Cottage, Renfrew, Renfrewshire
Barbara Duncan, Head, 79, born c1802, Kelso, Roxburghshire
Barbara Duncan, Daughter, age 41, born c1840, Renfrew, Renfrewshire
Anne D. Duncan, Daughter, age 33, born c1848, Renfrew, Renfrewshire
Mary W. Duncan, Grand Daughter, age 15, Pupil Teacher, born c1866, Renfrew, Renfrewshire
(Mary Woodrow Duncan, daughter of Robert Duncan & Martha Kirkham Lees, born 10th February 1866, Govan, Lanarkshire)
1891 Census (transcription), Living at Clyde Bank Cottage, Renfrew, Renfrewshire
Barbara Duncan, Head, age 53, born c1838, Glasgow, Lanarkshire
Ann Duncan, Sister, age 42, born c1849, Renfrew, Renfrewshire
1901 Census (transcription), Living at Clyde Bank Cottage, Renfrew, Renfrewshire
Barbara Duncan, Head, age 64, Housekeeper, born c1837, Glasgow, Lanarkshire
Ann Duncan, Sister, age 54, born c1849, Renfrew, Renfrewshire
I think some 'sideways' research will be required to find the births you are looking for and hopefully, you'll be able to find these elusive births.
Good Luck!
Anne
