A benefit concert will be held in Oshawa, Ont., on Thursday to raise money for a family forced to pay $80 a day for a special formula not covered by the provincial government to feed their young twins.

Shaylyn and Grayson Grant have a rare digestive condition known as necrotizing enterocolitis (NEC). Doctors discovered the condition after Shaylyn began vomiting blood a couple of days after she was born on Jan. 28. Her parents also noticed blood in her stool.

Soon after, Shaylyn's sister, Grayson, also showed similar symptoms.

"That's when they decided, after more testing and bowel sounds, that they have necrotizing enterocolitis," the girls' mother, Jamie Barrette, told CTV Toronto.

Often seen in premature infants, NEC can cause perforation of the bowels and lead to life-threatening infections as a result of the dairy-related components in their mother's milk.

Barrette said she tried eliminating dairy from her diet to help her twins digest her milk, but the Bowmanville, Ont., mother wasn't able to produce enough food for her two girls. The family then switched to formula.

They eventually found Neocate, an amino-acid based, hypoallergenic formula for infants. To feed both Shaylyn and Grayson, the family is paying $80 a day -- a cost not covered by OHIP as the formula is not considered a medicine.

The girls' father was initially told the formula would be covered by his insurance, but the company later told them they had made a mistake and Neocate isn't covered as it's considered a supplement.

"It's their only source (of food) but they say it's a supplement," Barrette said. "That's their loophole."

So far, the Ontario family has been relying on the generosity of their community to help cover the $80 a day cost -- a figure that's expected to grow as the twins get older.

Doctors say Grayson will likely be on Neocate for at least a year, but it's still unclear how long her sister, who has more damage to her digestive tract, will need it.

The family is hoping to raise $3,000  Elton Rohn, an Elton John tribute singer will be performing at the event.

With a report from CTV Toronto's Pauline Chan