Samantha Rigg-David, the sister of Sean Rigg, a 40-year-old man who died in police custody in 2008 in Brixton, and Alastair Morgan, whose brother Daniel - a private detective - was found with an axe in his head in a south London pub's carpark in 1987, took part in the demonstration.
The schoolboy was shot in the carpark of the former Fir Tree pub in Croxteth when he was caught in the crossfire between two gangs as he left a nearby football pitch.