Toshiko Sato's brother
From Tardis Wiki, the free Doctor Who reference
Toshiko Sato's brother died. The computer virus attempted to upset Tosh by accusing her of abandoning her brother to his death. It was because of her guilt that she was so desperate to save Max. (AUDIO: torchwood_cascade_CDRIP.tor)
Behind the scenes
Toshiko mentioned her brother in a deleted scene from the episode Captain Jack Harkness.
