A father from Ontario is facing impossible news: He's a liver transplant match for his 3-year-old twins, both of whom suffer from the same life-threatening disease, but he can only donate his tissues to one of them.

The Canadian couple, Johanne and Michael Wagner, adopted the twins from Vietnam in 2012, knowing of the girls' illness. "We were willing to go through with the adoption, thinking at least we could give them the love of the family and be able to hold their hand until the very end,” Johanne told the CBC, a Canadian news organization.

The sisters, Binh and Phuoc, suffer from Alagille syndrome, a genetic disorder that causes irregularities in the liver that can lead to a dangerous build-up of bile that severely damages the organ. The disease is also associated with heart defects, kidney disease, and physical abnormalities, but the effects on the liver are often the most serious.

Because of the severity of the Wagner twins' syndrome, drugs and other interventions are no longer helping—both girls need a liver transplant. The couple recently found out that Michael is a match for the girls, so he can be what's called a "living donor." These types of transplants are most commonly done with kidneys, but it's possible with the liver (as well as the lungs and pancreas) because the organ can regenerate.

Sadly, though, in order for the surgery to be safe for him, surgeons can only remove a small part of his liver, and he can only do it once because of the way the tissue regenerates.

Doctors at Toronto General Hospital will make the final call as to which child will receive a portion of Michael’s liver, factoring in the severity of each girls’ condition. “We told them we didn’t want to be burdened with the decision-making,” Joanne told The Globe and Mail. The first operation is expected to take place within the next few weeks.

While this is anything but easy for the parents, they are sharing their story to raise awareness about live donors and hoping that a liver soon becomes available for their second daughter. Joanne says they've already received hundreds of message from willing volunteers via a Facebook page the couple set up, ABC News reported. The Wagners are referring all who are interested to Toronto General Hospital to see if they're a match.

Receiving a portion of a liver from a living donor comes with many benefits. It usually lasts longer than a liver from a deceased donor, and there is little to no waiting period—whereas there are nearly 17,000 people currently in the United States waiting for a liver transplant. To be a live donor you don’t necessarily have to be a family member of the recipient, but many hospitals want donors that share some sort of an emotional relationship.

The surgeries do not come without serious risks. For donors, complications like infections, blood clots, damage to surrounding tissue or organs, or even death are possible, according to the American Transplant Foundation. And recipients face the same, plus the small chance of rejection that comes with any transplant.