Some siblings share their toys, a room or sometimes even a bed. The Demasi brothers will share a lot more.
Michael Jr. is just 4 years old and is going to help his baby brothers get a much-needed bone marrow transplant.
The twins, Santino (called Sonny) and Giovanni (or Gio), have a rare disorder called chronic granulomatous disease or CGD. It causes the immune system to malfunction, according to the National Institutes of Health, leaving patients unable to fight infections.
The solution: a bone marrow transplant.
The perfect match: their older brother, Michael.
The surgery is scheduled for Thursday. But this week, the twins began a 10-day chemotherapy regimen. The transplant is a risky procedure, but their mother, Robin Pownall, will be there throughout the entire thing, hoping for the best.
"I try to stay positive for them," she said. "I feel like that'll help them get through this better."
Sonny and Gio, born October 14, were diagnosed with CGD just 10 days after they went home from the hospital. The disease affects nearly 6,000 people in the US and Europe, according to the CGD Society.
The disease is hereditary. It is more prominent in boys because it affects the X-chromosome. Boys have only one of these, so if an affected gene is passed down by their mother, they will have CGD.
"Typically, a mother is a carrier and passes it to her son," said Dr. Jennifer Leiding, an associate professor of pediatric immunology at the University of South Florida, who is not involved in the boys' care.
Most parents go through this process only once. But Dominick, 9, Pownall's oldest son, was also diagnosed with CGD. He was not cured until he received an umbilical cord donation from a stranger the day before his 1st birthday. This gave Dominick the stem cells he needed to boost his immune system.
"Umbilical cord blood transplants are essentially the same procedure" as a bone marrow transplant, Leiding said.
Dominick's transplant was eight years ago, and now, his 4-month-old brothers need the same thing -- but this time, Michael will be the hero.
The twins remained in intensive care at Lankenau Medical Center, where they were born, for five weeks. After their diagnosis, they moved to the Children's Hospital of Philadelphia.
Pownall, who has stayed with the twins, has had to wear a mask and hospital gown around them to limit infections. She admits she's sneaked in some kisses. Now that chemo has started, she doesn't have to do that anymore.
Pownall said Michael constantly reminds the twins how much he loves them. Now, he will have the chance to show them by helping save their lives.
A perfect sibling bone marrow match is better than an umbilical cord stem cell match, so the family told Michael that they were going to take his blood to see whether he was even a possible match.
"He was on board since the minute we told him," Pownall said. "He knows it's going to be a big needle going into his back."
When they got the call, Pownall knew that it was good news. But she didn't expect the twins to match each other; she worried that Michael would match only one of the two.
Many people say Michael doesn't understand what he's going to go through, but his mother believes that's not true.
"He knows. He's a very smart boy," she said. "He's fearless, and he wants to save them."
And on Thursday, if all goes as planned, Michael Jr. will walk out of the hospital after the procedure. His brothers will be able to head home four to six weeks later.
As soon as the transplant is over and everyone is healed, the family wants to go camping and fishing. Michael, though, has different plans.
"Michael says he wants to go on an airplane," Pownall said with a laugh. "He says, 'I want to go on the airplane to Ghostbusters.' "
Ghostbusters -- what he calls the restaurant and game arcade Dave & Busters -- is about a mile from their house, Pownall explains.
"Maybe we'll take him to Disney eventually," Pownall said.
What's most important to them, they say, is that Michael is a hero at age 4 and is selflessly helping his baby brothers.
Pownall said that one should always believe, always have hope and stay positive.
"And hopefully, if you remain positive, things will turn out positive," she said.
Sonny and Gio Demasi have a rare disorder called chronic granulomatous disease
Their older brother Michael Jr. is a perfect match and is excited to help