A Quebec couple is reeling after their young daughter was diagnosed with the same type of rare cancer their older son fought eight years ago.

Four-year-old Sophia Randell now has the same aggressive cancer her older brother, Jacob, was diagnosed with at age 5.

“It was the size of a golf ball,” Jacob says of the tumour that doctors found in his brain. Jacob underwent surgery, chemotherapy, radiation and a transplant. Now 13 years old, he is in remission.

“We almost lost him, he was dying,” said his mother, Liliane Hajjar. “But we found our happy place.”

The hereditary cancer is linked to the kids’ father Jason, who has a genetic mutation that causes benign tumours in his body. It's a rare tumor syndrome called hereditary Schwannomatosis, which Jason had been diagnosed with years earlier.

After Jacob’s diagnosis, the entire family, including middle sibling Liam, underwent genetic testing at the Children’s Hospital of Eastern Ontario.

Geneticists there found it was an inherited condition caused by a mutation in the SMARCB1 gene, which can also lead to aggressive malignant tumours in infancy.

While seven-year-old Liam tested negative, Sophia tested positive for the gene mutation. Since that initial test, Sophia has been monitored with regular MRIs and ultrasounds.

The test results were always fine, until last November, when a tumour was discovered on the left side of Sophia’s brain, in the exact same location as Jacob’s.

“One child diagnosed with cancer is absolutely devastating but two is life-changing,” Hajjar told CTV Ottawa.

Since then, Sophia has undergone a transplant and is currently receiving chemotherapy.

Jacob said if he could, he would fight his little sister’s cancer for her.

"I’m like, ‘Why her? Why not me, again?'” Jacob said. “Because if it was me again, I’d be able to do it, it wouldn’t be too hard because I’ve already been through (it).”

All three siblings share an unusual bond and a deep appreciation for each other.

“I have a new will to live,” Jacob said. “Because if I die, I wouldn’t be able to see Liam grow up and then eventually, Sophia.”

CHEO geneticist Dr. Eva Tomiak said that while it’s difficult to see a child as young as Sophia receive a cancer diagnosis, “we hope that we’ve made a difference in terms of finding it at an earlier point in time.”

Sophia isn’t in remission yet, but family and doctors are hopeful that by catching it early, they’ve given her the best possible chance at recovery.

The family says they share a deep appreciation for life and for the good things still to come.

“We know that we’re going to find our happy place and we’re going to be OK,” said Hajjar. “I know it, I feel it.”

With a report by CTV Ottawa’s Joanne Schnurr