No Agnes Graham found with parents William & Jane Watson. The only Agnes Graham born in Scotland recorded in 1850 was
GROS b 23/06/1850 GRAHAM, AGNES
parents ANGUS GRAHAM/CATHERINE MCMILLEN
Dalry (Ayr)/AYR 587/ 0030 0159
Joy’s contact had following birth
Agnes (Graham) [F William M Jane Watson] b 3 May 1850 Dundee Angus
Which probably fits with below 1851 census (mother Janet
Name:Agnes GrahamAge: 1
Estimated birth year: abt 1850
Relationship: Daughter
Father's Name: William
Mother's Name: Janet
Gender: Female
Where born: Dundee, Forfarshire
Parish Number: 310
Civil parish: Monifieth
Town: Broughty Ferry
County: Angus
Address: Queen Street
ED: 5
Household schedule number: 4
Line: 17
Roll: CSSCT1851_67
William Graham 33
Janet Graham 29
Euphemia Graham 7
Margaret Graham 4
Agnes Graham 1
Source Citation: Parish: Monifieth; ED: 5; Page: 17; Line: 1; Roll 1110; Year: 1851.
Assuming Janet Watson was mothers name the following is marriage
Groom's Name: William Graham
Bride's Name: Janet Watson
Marriage Date: 07 Apr 1843
Marriage Place: Newburgh,Fife,Scotland
Indexing Project (Batch) Number: M11450-5
System Origin: Scotland-ODM
Source Film Number: 1040169
Reference Number:
Collection: Scotland Marriages, 1561-1910