Thanks for the interest, Lones.
Yes, I do know the children.
They are two of his grandaughters;
Myra (age one) and Audrey (4 months) - cousins to my father.
Myra died in 2002, aged 92.
Great-grandad was a 'late starter' - he was born in Sheffield, Uk in 1825 and didn't marry (in NZ) until 1866, age 41. He was sixty when his last child was born - the mother of the older baby in the photo.
He died one year after this photo was taken, age 86. (He would've probably lived a little longer if he hadn't been hooked on his own medicine).
Ed