There is definitely a connection here.
Your Br Leo is the grandson of John who was in the RIC before moving to Australia. John had a brother Dominic.
I have these people in my tree. I also have their parents, Michael & Bridget. They lived in Marnellsgrove, near Ballymoe, Co. Galway.
I did not realise that there was more than two brothers. Can I ask where you found the records for this family?
Do you have any more information on the brother who stayed in Ireland? Birthdates or spouse?
Thanks and welcome to the family.