The Northamptonshire teenager's mother, father, step-parents and brother all came to Brackley to thank the Justice4Harry supporters in the less-than-ideal weather conditions.
South Northamptonshire MP Andrea Leadsom joined the crowd of people on Buckingham Road Industrial Estate to wave off the motorcyclists there to honour the young biker.
The cavalcade went around the area before passing RAF Croughton, where more people gathered for the vigil, and the nearby site of the crash last year.
Harry's dad, Tim Dunn, said: "To be honest we were all dreading the anniversary of Harry’s death. It is too painful to think about what happened to him this time last year. None of the parents planned to be there.
"But when we saw the terrible weather yet how many bikers and supporters were coming out we felt we needed to be there for them and to thank them for showing so much love to Harry.
"He was every bit as much a part of the biker family as our family. We couldn’t believe the incredible turnout and the outpouring of love for our son.
"It was a spectacular site to see. It helped ease our indescribable pain very slight and for that, on behalf of my whole family thank you from the bottom of our hearts.
"We know we have turned a corner in our fight for justice and can now sense that it is in touching distance. Please continue to support us. It really means the world."
Anne Sacoolas, the American driver who admitted to causing the accident by being on the wrong side of the road, remains in the United States having claimed diplomatic immunity.