Five riders have now been killed while racing at this year's Isle of Man TT event.
The latest riders to die were a father and son team competing in a sidecar race.
Roger Stockton, 56, was driving and his son Bradley, 21, was in the passenger seat.
Speaking earlier this year, Roger said: "I've retired a few times before, but always come back for my love of the sport. Going around the course with my own flesh and blood will be incredible."
The pair, from Crewe, lost their lives after an incident at Ago's Leap on the final lap of the second sidecar race.
It was Roger's 20th race in his 11th TT appearance. Bradley was competing in his second race in his maiden TT.
They were eighth in the first sidecar race.
The event organisers said: "We extend our deepest sympathy to their families, loved ones and friends."
They added: "The loss of two members of our paddock and two people from the same family is truly heart-breaking, but the bond between a father and son who achieved their dream to compete together at the TT provides us with a glimmer of light at such a dark time."
Crewe FC paid tribute to Bradley, saying the club was "devastated and deeply saddened" to learn the news.
They added: "Our heartfelt sympathies & thoughts are with his family, his friends and his teammates, all of whom will both miss him and love him immeasurably."
Hauliers Cooper Buckley Ltd said Roger had been part of their work family for over 20 years and will leave a "huge hole" in the company.
Roger Stockton made his TT debut in 2000 and competed regularly until 2008 before returning in 2010, 2017 and this year.
Organisers said that although it was Bradley's first TT as a competitor, it was by no means his first experience of the event, having made his first visit as a one-year-old.
When he was aged 16, he decided he wanted to follow in his father's footsteps and asked if he could race alongside him as his passenger. Once he had returned to the Isle of Man to begin studying the course, he said "he couldn't wait to race in the TT".
Welsh rider Mark Purslow was killed in qualifying last week, while Northern Ireland's Davy Morgan died after an accident in the Supersport Race on Monday.
Cesar Chanal, from Lyon in France, died last Saturday in a crash during a sidecar race.
Organisers originally announced his French passenger Olivier Lavorel had been killed before apologising for their error.