One-year-old Alle Jilg met the stranger who saved her life in May.
Born with severe combined immondeficiency (SCID) - often referred to as the rare 'bubble boy disease,' Alle needed a bone marrow transplant to give her some of the immune system she was born virtually without.
Luckily, a donor whose marrow matched hers was registered with Be The Match.
In February, Alle underwent a successful transplant and her parents, Mike and Tia got in touch with Jacob Oswald, a father-of-two whose donation had saved their own daughter's life.
The two families united for the first time, telling Good Morning America they felt like one family as Jacob held grinning baby Alle.
Jacob Oswald smiles as he meets Alle Jilg, the one-year-old with SCID who received a transplant of his donated bone marrow in Nebraska earlier this year. Alle's parents, Tiah and Mike (right) said they feel as though Jacob is already part of their own family
Alle's parents describe her as the 'light of her family,' and the bubbly infant seems totally unaware of her rare disease.
But, just a week after she was born, Alle's parents were given the devastating news that their little girl's life would be in danger if she came into contact with viruses or bacteria that would give most children nothing worse than the common cold.
SCID is a broad term for a set of multiple immune deficiencies, caused by genetic defects.
They are born with low counts of or no white blood cells that defend most of us from infections.
The disease also renders medications that would normally treat serious infections like pneumonia, meningitis or sepsis ineffective, making these particularly deadly.
Even less severe infections like the chickenpox, however, can be dangerous to the one in 58,000 babies born with SCID every year.
Despite her rare disease, Alle has always been a happy baby and the 'light of the family,' her father says
Because she has SCID, Alle has to avoid all sources of infection. A marrow transplant will allow her to develop an immune system
Often called 'bubble boy disease,' children who don't get bone marrow transplants have to be shielded from much of the world to protect them