He wasn't the only member of my family to have taken part in WWII. Six of my Dad's uncles also saw action – in North Africa, Asia and Europe.
One of them was awarded the Military Cross for his bravery under fire. Another was killed by a sniper in Germany a week before the war ended.
When my grandfather died five years ago, he left piles of papers and letters dating from the war.
From these, we discovered that we had another relative who had also been caught up in combat, our cousin William, a shy man with a severe stammer. Unlike other family members, William was not part of the Allied armed forces.
Instead, he was an Irish merchant seaman whose ship was sunk off the coast of Madagascar in August 1940.
After his ship was sunk, William was sent back to Europe as a prisoner of the Germans. He spent the next few years in various prison camps in Germany.
Then, in January of 1943, he and 31 other Irish merchant seamen were taken out of an internment camp, and asked by the Gestapo to volunteer to work for the Nazis.
These seamen came from most of the major ports in Ireland: Galway, Waterford, Wexford, Arklow, Tralee, Dublin, and Cork.
When they all refused to collaborate, they were sent to work as slave labourers in a concentration camp near the village of Farge in north-west Germany.
The camp had previously been used as a fuel depot by the German Navy.
The Irish seamen were badly beaten by their SS guards after they arrived. They were told that, from then on, they would have no contact whatever with the outside world.
For the next two years, they were subjected to a regime of great brutality and degradation.
When Red Cross officials were eventually allowed to visit them, they reported that the Irish prisoners lived in a state of "constant fear", with SS guards who were "prepared to shoot them under the least provocation". The Irish seamen had been brought to Farge to work on the construction of a huge fortified bunker.
The Nazis hoped to build a new type of U-boat that was bigger, faster, could dive deeper and had more fire power than any previous model.
Between 1943 and 1945, a slave labour force of more than 12,000 worked around the clock to build this colossal bunker.
However, it was still incomplete when the war ended: no U-boats ever left its pens.
Despite that, it is believed that almost half of the slaves who worked at the bunker died there – from starvation, exhaustion, disease or by murder.
One of those who died was William.
According to one of the survivors, he had been ill for a few days when the doctor who attended the camp decided to operate.
The operation took place on a table that had not been sterilised, and there was no anaesthetic. Instead, William was held down by four of his fellow Irish prisoners. He died in the early hours of the next day.
All the 32 Irish seamen held in the camp were non-combattants from a neutral state. Their detention was illegal, and they all should have been repatriated.
However, Ireland's diplomats in Berlin showed no apparent interest in securing their release until very late in the war – too late to be of any practical benefit.
This indifference to the fate of its own citizens was shared by the Irish government of the day.
Some of the Irish slave workers returned to Ireland in May 1945, but there was little official interest in what they had suffered, and they disappeared from public view.
Sadly, it wasn't only these merchant seamen who were neglected when they came back to Ireland.
Many of the Irish men and women who took part in the war against Nazism were also isolated, and sometimes ostracised when they returned.
But the Irish merchant seamen who were forced to work as slaves haven't been forgotten in Germany. Part of the bunker in Farge is now a museum, and there is a section devoted to the Irish seamen.
My father has written a book, Suddenly, While Abroad, telling the dreadful story of what happened to William and the 32 Irishmen in Farge.
I hope that it will also serve to honour the memory of the 32 Irish seamen who refused to collaborate with the Nazis – and paid such a high price as a consequence.
Suddenly, While Abroad: Hitler's Irish Slaves by David Blake Knox (New Island Books) is in shops now priced at €16.99