When Molly Duffy and Robbie Edwards, both 3, met in person for the first time at Boston Children’s Hospital in November, it was like they’d been best friends forever.
The tiny tots, who both have light brown hair, sparkling blue eyes and infectious, toothy grins, could pass for sisters. They both love listening to “Wheels on the Bus,” playing house in their miniature toy kitchen sets and spending time outside.
But another commonality unites the toddlers, who are the only known people in the country, and two of 11 in the entire world, diagnosed with an extremely rare disease called SPG-47 or hereditary spastic paraplegia type 47 that causes a decline in everyday cognitive and physical functions.
Doctors say their symptoms, which currently include difficulty walking and talking, will worsen over time — most likely shortening their lives.
“They’re in this fight together,” says Robbie’s mom, Kasey Edwards, 38. “Their futures are intertwined, as we look to the future.”
When doctors told Kasey and her husband Chris Edwards, 41, about their daughter’s rare diagnosis in May 2016, they felt devastated and alone.
“It was surreal. We wept and said, ‘This can’t be,’ ” says Kasey, also mom to 5-year-old son Davis. “No one knows much about the condition, so we knew our world would be completely changed. But we weren’t going to let it derail our train.”
The Boston parents began researching Robbie’s SPG-47 diagnosis, a particular subtype of hereditary spastic paraplegia that, in addition to causing the progressive decline of motor functions, leads to severe cognitive delays and microcephaly. They found only nine other known children with the condition and none were in the U.S.
But, in what they describe as a “miracle meeting,” Kasey and Chris connected with Molly’s parents Angela and Kevin Duffy, both 33, in August through a Facebook support page for parents of children with SPG.
“We thought she was the only person in America with this type of SPG,” Angela tells PEOPLE of Molly, who was diagnosed with SPG-47 a year ago. “There are over 50 types of SPG, but Molly and Robbie are the only ones with type 47. Until we found Robbie, we thought we were so alone in this journey.
“But now we have each other.”
On Nov. 14, after two months of daily texts, e-mails and video chats, Angela, Kevin and Molly flew from their Hatboro, Pennsylvania, home to meet the Edwards in person at Boston Children’s Hospital, where both girls have been patients.
For more on Molly and Robbie, pick up the latest issue of PEOPLE, on newsstands Friday.
While the girls played together at a toy kitchen, the stark reality of their uncertain future tugged at their watchful parents, who have been working to find a cure for SPG-47 ever since they met online.
Molly uses a walker to move and her progressive symptoms include developmental delays and hypotonia — she knows around 200 words. Robbie, who has microcephaly, suffers from complex seizures, delayed motor skill development and can speak almost 50 words.
“We weren’t satisfied with the lack of knowledge about this condition,” Kevin tells PEOPLE. “Now we are all working together to save our girls.”
Disappointed with a limited amount of research available in the medical community, the families are setting up a non-profit called Cure SPG47 to raise money for research, working closely with doctors from Boston Children’s and SPG experts from the University of Michigan, including SPG expert Dr. John Fink.
“We need more people to study this,” says Chris. “We’re running Cure SPG47 together to help our daughters survive.”
And the Edwards and Duffys won’t give up until they get some answers.
“We wept with this rare diagnosis, but dried our tears quickly,” says Kasey. “We will never stop fighting and we will never give up on our girls.”