The family of Kurt Cochran refused to condemn the killer
US tourist Mr Cochran never had harsh feelings for anyone in his life and his relatives say they will draw strength from his example.
The man President Donald Trump called "a great American" was mowed down by Khalid Masood as he smashed into pedestrians on Westminster Bridge in a 4×4 Hyundai.
The impact hurled Mr Cochran, 54, over a bridge parapet to his death in last Wednesday's atrocity.
His wife Melissa, 46, suffered a serious leg injury when Masood ploughed into her but is recovering in hospital.
It has been a tender experience for our family to be together with Melissa here
The couple, from Utah, were on the last day of a European trip to celebrate their 25th wedding anniversary when Masood struck.
In a moving Scotland Yard conference, the devout family told how they have been "humbled" by messages of sympathy from all over the world.
Mr Cochran's brother-in-law Clint Payne said: "It has been a tender experience for our family to be together with Melissa here.
"Her health is steadily improving and she has been strengthened by the presence of her family.
The family told how they have been "humbled" by messages of sympathy
"She is so grateful for the outpouring of love and generosity.
"So many people have been so kind and we are deeply touched by their goodness and generosity.
"Your notes, prayers, donations and love have helped us so much."
Flanked by 12 family members, Mr Payne paid tribute to music producer Mr Cochran.
Mr Payne said: "The most difficult part of all of this is that Kurt is no longer with us, and we miss him terribly.
"He was an amazing individual who loved everyone and tried to make the world a better place.
"He left a legacy of generosity and service that continues to inspire us.
"We are deeply saddened to lose him but are grateful that the world is coming to know him and be inspired by him."
The couple were on the last day of a European trip to celebrate their 25th wedding anniversary
The couple, who ran a recording studio in West Bountiful, Utah, travelled around England, Scotland, Ireland, Holland, Germany and Belgium during their anniversary trip.
Their last day was to be spent sight-seeing in London following a visit to Mrs Cochran's parents Dimmon and Sandra Payne who are UK-based missionaries for the Church of Latter Day Saints.
Mr Payne said: "Kurt loved it here. He said he felt like he was at home."
He added: "Kurt would not carry ill feelings towards anyone.
"We can draw strength as a family from that. His life was an example of focusing on the positive not living out life in the negative."
Mrs Cochran's sister-in-law Sara McFarland spoke for all the family saying: "None of us harbour any ill will or harsh feelings towards him.
"We loved our brother and what he brought to the world. This situation will bring many good things to the world."
Mrs Cochran's mother said it was "heart-wrenching" see a picture of her daughter lying on the bridge in the immediate aftermath of the attack.
London mourns terror attack at vigil Fri, March 24, 2017
The world grieves after an attacker killed three people and injured about 40 near parliament in London.
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Floral tributes are left after the vigil in Trafalgar Square, London to remember those who lost their lives in the Westminster terrorist attack
Mrs Payne said: "But every day I have seen her get stronger.
"We saw her yesterday and she did have the strength to talk about Kurt and we could laugh together. It was wonderful."
Jennifer Burton described her sister as "fun, strong, happy and feisty" adding: "She's a fighter."
Mrs Burton said: "She is just going along wonderfully. She is happy to be alive. Although she has lost her love, the world will get to know him."
They spent their last day sight-seeing in London
Mr Cochran's murder and the serious injury to his wife was "horrible and gut-wrenching," Mrs Cochran's sister-in-law Shantelle Payne said.
The family had rallied round to support the bereaved widow as she recovers, she added.
Mr Payne paid tribute to the emergency services and thanked Delta Airlines for arranging travel to and from London.
He said: "Your notes, payers, donations and love have helped us so much."