descendants of John McMillan & Grace Blue

[JOEMAC]

Hi there from sunny Australia.
I am trying to trace descendants of JOHN McMILLAN [born Achalochan 1812] and his wife GRACE BLUE [born Killean 1815]
They married in Campbeltown in 1848 and had the following children all born in Campbeltown
JOHN McMILLAN b. 1850 [my grandfather]
DUGALD McMILLAN b. 1851
MARION McMILLAN b. 1854
DONALD McMILLAN b. 1859
If there are any descendants of Dugald, Marion or Donald anywhere i would love to hear from them.
Kindest regards,
Joemac