I am interested in your GGgrandfather Michael Hanrahan.
You mention you think he had a brother Patrick.
I have an ancestor called Margaret Hanrahan (1836 Clare).
Her brother Michael Hanrahan was known as Captain of the Pikeman in the Eureka Stockade.
I have their siblings as
John, Bridget, Maura, PATRICK and Thomas.
Margaret married Daniel Powell.
Their son Cornelius was my Ggrandfather.
Does this sound like a match?
Regards Kelly, Brisbane