Hello Lin, and Brevitas,
That is them in 1871. Brevitas, By 1881 John Pollock, is still in Bonhill, Dunbarton, this time he has a Margaret, as his wife, most likely Isabella Murray Pollock, died in perth sometime after the birth of Jane Pollock,1869. their last child.
Maybe Isabella Pollock, got her mothers first name mixed up on her marriage certificate, the young John Pollock, age 7 years on the 1871. census born Perth, fits well with the John Pollock, born 1863, Perth, to John Pollock, and Isabella Murray.
Regards,
Jonn.