Suzanne Kreiter/Globe staff

Behaylu Barry tickled his 9-year-old sister's feet. The 13-year-old boy was adopted by a New Hampshire couple. He seemed to have endless reserves of energy until February.

Suzanne Kreiter/Globe staff

Tests revealed Behaylu has severe aplastic anemia, a life-threatening disease. The diagnosis set off a mission that reached his native Ethiopia and reunited him with a brother and sister. Pictured: Eden (from left), Behaylu, and Rediat posed in front of Midori Kobayashi and Aidan Barry.

Suzanne Kreiter/Globe staff

Kobayashi and Barry brought Behaylu home to New Hampshire in the summer of 2007.

Suzanne Kreiter/Globe staff

Behaylu played soccer with his 16-year-old brother. The illness ravages stem cells in bone marrow that produce the key components of blood and is so rare it strikes only two or three people out of every 1 million in the United States each year.

Suzanne Kreiter/Globe staff

Siblings have a 1 in 4 chance of matching. Pictured: Eden, 9, dressed her hair.

Suzanne Kreiter/Globe staff

Behaylu's parents sent test kits to his biological family, and a Red Cross lab in Dedham confirmed that two of his birth siblings were perfect matches.

Suzanne Kreiter/Globe staff

They worked with their US senators to expedite passports and visas for the two village children, who lacked birth certificates. Pictured: Barry with Eden.

Suzanne Kreiter/Globe staff

In a week, Rediat — with his sister as backup — will undergo anesthesia so doctors can extract marrow from a hip bone using a long needle. The stem cells from that marrow will then be infused into Behaylu’s bloodstream, to find their way into his bones.

Suzanne Kreiter/Globe staff

Behaylu played with Eden in the family room.

Suzanne Kreiter/Globe staff

Behaylu was eager to take his brother and sister on a tour of his school, where the teachers and seventh-graders greeted him like a celebrity.

Suzanne Kreiter/Globe staff

Behaylu put his arm around his sister during a tour of his middle school.