Tonight he will be in the Aviva Stadium for the sell-out Leinster v Munster Rabodirect Pro12 clash.
He and his wife Jenny welcomed their third child, Robyn, last year.
The 34-year-old and his other half have two other daughters, Sophie and Anna.
He told the Herald that with so many away matches playing for Munster and Ireland over the years, he misses out on time with his girls.
"It's tough because of what I do to work. You have to travel a lot and that's a hard part of it – you're living out of a gear bag most of the time and you miss what's happening at home," he said.
"But at the same time you're living your dream, and my family really supports me. I'm lucky too that Sophie is three now and she's starting to get into rugby a little bit."
The Corkman said tonight's game will be far more enjoyable for the fans than for the players on the pitch.
"We'll all just be wanting to get to the other side of the game with a win. Even if it's just by three points, everything will be contested," he said.
O'Callaghan took time out from the training ground yesterday to show his support at UNICEF Ireland's Mother's Day Lunch in the Shelbourne Hotel.
He is an ambassador for the charity, and said while he has had the privilege of wearing a green jersey, he was more proud to be Irish when on a recent UNICEF trip to Syria.
"I've never felt such pride in being an Irishman than when I was over on that visit. The people there noticeably softened to us because they know that Irish people help out in a big way," he said.
SEE SPORT, PAGES 54-55