Diana Rios said her brother, Andres Adams, was supposed to begin fifth grade next week in Fallbrook, which is near San Diego.
Andres and his 6-year-old half-brother, Jacob, were swept away while cooling off in the Merced River last week. Jacob's body has not been found, and he is presumed dead.
Rios said Andres loved people, soccer and ice cream.
"The way he looked at life, I guess, it was like, it was different. You knew he was special," said Rios.
The brothers and their parents had gone to Yosemite with a church group based out of Anaheim. Andres' stepmother remains hospitalized with a spine fracture. Andres will be laid to rest Thursday.