I can see 2 daughters born to George & Catherine in Victoria:
Agnes Elizabeth McKellar GRAHAM 1857/11899 Dunolly
Jane Stephen GRAHAM 1859/15824 Sandy Creek, d. 1860/3295 aged 8 months
Likely death of George, given his mum's name:
Given Names: George
Mother: Jane STEPHEN
Birth Place: GLAS
Reg Number: 7039
The Argus, Monday 5 August 1878
A very sudden death occurred last night.
A man named George Graham, whilst sitting in the Corner Hotel, fell down, and immediately expired. An inquest was held today before Mr B. Smith, police magistrate, at which it was elicited that deceased had not been in good health for some time previously. The medical evidence went to show that the cause of death was a fibrous clot on the walls of the heart, thereby leading to coagulation of the blood, and causing cessation of the heart's action. The jury returned a verdict according to the medical testimony.
Given Names: Cath
Father: Stewart Jno
Mother: Agnes MCKELLAR
Death Place: Tgulla
Reg. Number: 11632
I can't find a marriage for daughter Agnes.