Businessman Bernard Byrne sells Catholic religious goods from his shop in the Co Mayo village of Knock.
His grandfather, Dominic Byrne Senior was one of the visionaries of the apparition in Knock in August 1879.
His family are the last remaining descendants in the village of the 15 witnesses who saw a light coming from the parish church on that rainy night.
On the gable wall they saw an apparition of the Virgin Mary, St Joseph and St John the Evangelist.
Bernard never met his grandfather but his story remains an integral part of their family history.
“My grandfather’s story has always been with us,” he said.
“It’s very important I pass it on to my family. I have written it down and documented my memories.
“At that time Knock was a very small place, it was like a little hamlet and all the families who lived in the vicinity of the church all saw the apparition.
“After the apparition they nearly had to open a bed and breakfast when all the pilgrims came.”
Many of the families opened up their homes to the people who descended on Knock after the apparition in the hope of finding a miracle cure for ailments and disabilities.
“My family saw people being brought in on stretchers in to their kitchen, then going to the shrine and leaving the stretchers behind them,” he added.
“They came to the house to see my grandfather and be near the shrine.
“Knock has changed completely and the apparition has brought a lot of wealth into the area.
“After my grandfather died, people wanted to talk to my dad all the time as he was the next in line.
“I’m very proud of it and I’ve always said theologically it’s a phenomenal apparition.”
Bernard is one of 40 choir members who will be singing for the Pope when he visits on Sunday.
They have been practising three nights a week to prepare for the Pontiff’s arrival.
He said that despite his grandfather’s place in the history of Knock, it has had little influence on his religious beliefs.
“We always had great faith,” he said.
“It didn’t make us any more religious.”
Speaking from his shop where he sells religious statues, memorial cards, books and rosary beads, Bernard describes the excitement sweeping through the village ahead of the Pope’s visit.
“The village has had a great clean up, nearly everything has been done.
“Almost 20 million euro has been spent on the church in the last three years and I think once they announced the Pope was coming to Dublin they expected him to come to Knock.
“All the houses around the village have been painted, there’s bunting up all around and flowers have been planted so it has got a great facelift just for the Pope.
“It has been a massive community effort and with the Church authorities and Co Mayo council.
“You can feel the atmosphere in the place, there is something extraordinary happening in the place.
“We are so delighted and feel a great honour by him coming to the shrine.”