Brian O'Shea smiles at his son Torben as the baby happily gurgles and squirms in his mother Maria's arms.
The couple say the one-year-old gives them hope and light as they try to live with the loss of their children Soren, 11, Saoirse, 9, and Connor, 3.
But Mr O'Shea admits happy moments with Torben can be tempered by sadness when the sight of him in one of his brothers' T-shirts evokes memories of the others.
"They look so similar and it's such a flashback to his brothers, it can be very poignant," Mr O'Shea said.
"When that feeling comes, it can take away from a moment that should otherwise be joyous and can detract from him being him."
The O'Sheas said Connor, the family's little ragamuffin, had thought Torben was a gift for him when he was brought home from the hospital.
Soren, who would have turned 12 last month, was thoughtful and caring, while Saoirse was bright, happy and inquisitive.
Dr O'Shea said 3pm was now an especially difficult time. "You can see all the other school kids come home and ours are not - that's a very hard period," she said.
The O'Sheas have formed The 3 Musketeers to honour their children and what they brought to their lives.
"We're trying to redirect our energy towards something positive and we want to help other children have better lives," Dr O'Shea said.
Mr O'Shea added: "We'd prefer to let our actions show people who we are and who our children were."
They are currently seeking unused hearing aids for children. "We want to offer hearing and the possibility of a normal life to children that otherwise are treated as fools because they cannot hear," Mr O'Shea said.
Details of other projects are at Www.3musketeers. net.au or Www.facebook. com/3musketeers