Hi Keera,
I couldn't find your Robert Paterson who married a Catherine Shaw, but I did find a Robert Paterson who married a Janet Shaw and according to the British Vital Records, they only had one child. (They may well have had more but this is the only one recorded to this couple):
PATERSON, Janet
Gender: Female
Birth Date: 3 Sep 1826
Christening Date: 17 Sep 1826
Recorded in: Denny, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Janet SHAW
Source: FHL Film 1041975 Dates: 1679 - 1855
The date of Alexander's marriage to Catherine Dawson - are you sure this was 28 years after his brother Robert's marriage?
Here's a list of all the births to Robert and Helen just in case you haven't got them already:
PATERSON, Thomas
Gender: Male
Christening Date: 25 May 1783
Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBUL
Source: FHL Film 1041956 Dates: 1688 – 1819
PATERSON, Robert
Gender: Male
Christening Date: 13 Mar 1785
Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBUL
Source: FHL Film 1041956 Dates: 1688 – 1819
PATERSON, Helen
Gender: Female
Christening Date: 7 Feb 1787
Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBUL
Source: FHL Film 1041956 Dates: 1688 – 1819
PATERSON, Christian
Gender: Female
Christening Date: 23 May 1790
Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBULL
Source: FHL Film 1041956 Dates: 1688 – 1819
PATERSON, Lily
Gender: Female
Christening Date: 6 May 1793
Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBULL
Source: FHL Film 1041956 Dates: 1688 – 1819
PATERSON, James
Gender: Male
Christening Date: 26 Oct 1795 Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBULL
Source: FHL Film 1041956 Dates: 1688 – 1819
PATERSON, Margaret
Gender: Female
Christening Date: 30 Oct 1797
Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBULL
Source: FHL Film 1041956 Dates: 1688 – 1819
PATERSON, Janet
Gender: Female
Christening Date: Jan 1799
Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBULL
Source: FHL Film 1041956 Dates: 1688 – 1819
PATERSON, Alexander
Gender: Male
Christening Date: 9 Dec 1802
Recorded in: St. Ninians, Stirlingshire, Scotland
Father: Robert PATERSON
Mother: Helen TURNBULL
Source: FHL Film 1041956 Dates: 1688 - 1819
I'm not searching this family but if there's any more lookups you'd like either on the BVR's of 1881 Cencus, just give me a shout.
Anne