Mohammed Sidique Khan, Shehzad Tanweer and Hasib Hussain, along with a fourth man Germaine Lindsay, detonated bombs in London killing 52 people in 2005.
Qari Asim, of the Leeds Makkah Mosque, said their families were still in "this sense of shock and disbelief".
He said an event retracing their steps would take place over the weekend.
Mr Asim, whose mosque is in the Hyde Park area of Leeds, said: "Ten years on and the Muslim community, and the wider community, we are all still looking for answers, we are all still trying to find out what are the factors and what is the evidence that leads to radicalisation.
"The families of those three men who came from Leeds and blew themselves up in London, they are still looking for answers because to them they would never have imagined that their young men would do something like that and they're still going through this sense of shock and disbelief."
He said the three were described as "ordinary young men, they were gentlemen, they were good to talk to, they were very friendly people effectively", he said.
"How can three young men, living their ordinary lives, become so radicalised? Can be so motivated that they can take their own lives but also take the lives of others?"
This weekend a group of young people from different faiths are to travel from Leeds to London retracing the steps of the three bombers.
The Leeds Peace Ambassadors will undertake a "peace journey" to mark the 10th anniversary of the bombings, hoping to inspire unity among different faiths.
Fifty-two people died and hundreds were injured when bombs exploded on three Tubes and a bus.
Thirteen victims were killed on the bus at Tavistock Square, 26 died in a bombing at Russell Square on the Piccadilly line; six died in an explosion at Edgware Road on the Circle Line; and seven died at Aldgate on the Circle Line.

The 15-year-old South Korea-born New Zealander finished with a five-under-par 67 to win by three shots.
She broke the age record of 16, set by Lexi Thompson in the Navistar LPGA Classic in Alabama last September.
Only four other amateurs have ever won on the Tour, and Ko became the first since JoAnne Carner took the 1969 Burdine's Invitational tournament.
In January, Ko won the New South Wales Open in Australia at 14 to become the youngest player to win a professional tour event, a mark broken by 14-year-old Brooke Henderson in June in a Canadian Women's Tour event in Quebec.
Ko also won the US Women's Amateur two weeks ago in Cleveland, Ohio.
Starting the final round at The Vancouver Golf Club one shot clear, she surged away from the field on the backward nine, shooting five birdies in six holes to finish at 13 under.
Inbee Park shot a 69 to finish second on 10 under, while US Women's Open champion Na Yeon Choi, Chella Choi and Jiyai Shin tied for third at eight under.
The families of three 7 July suicide bombers are still looking for answers 10 years on, an imam from their home city of Leeds has said.
[NEXT_CONCEPT]
Lydia Ko won the Canadian Women's Open to become the youngest tournament winner in LPGA Tour history.