My grandfather was William Percival Blunden, but I am not sure if this is the person you are looking for. He died in about 1972, and his father was called John, I think. His father ran a cram school to enable people pass exams for the civil service.
They lived in Charleston Road as it is called now, in Ranelagh and before that I think in Stamer Street off the South Circular Road. Willie had a sister Frances who went to live in England and married someone called Kerr. He also had a brother John and a sisters called Jenny (birth name Camilla, I think) who never married and a sister Mary (later called May) who married someone called Derham.
My grandfather married Eileen Kelly who came from Ranelagh (family ran a pub and grocers) and they initially lived in Leeson Street and then moved to Terenure. They had 2 children, Niall and Ailis (called Peggy).