Justina Rosa Botelho says 29-year-old Ali Moustafa of Toronto was killed in a bomb attack Sunday.
Botelho says she learned of his death after activists sent her a photograph of her brother's corpse. Botelho spoke to The Associated Press by telephone.
Aleppo-based activist Abu Hassan al-Marea also confirmed that Moustafa was killed after a crude barrel bomb landed near where he and firefighters were standing.
Syria is the world's most dangerous conflict for reporters.
Since the Syrian uprising began in March 2011, dozens of journalists have been kidnapped or killed by both forces loyal to President Bashar Assad and rebels seeking his overthrow.