Khan was attending the nuptials in Bolton, England on Tuesday (25Dec12) as a second cousin of the bride when news of the tragedy filtered through to guests.
It is believed the three who were killed - boys aged four and 10 and their 32-year-old aunt - when their car overturned on a major highway were guests of the groom and were not related to Khan, but the Olympic silver medallist has been left heartbroken by the horror.
He tells British newspaper The Sun, ""My heart goes out to the families of those involved in this terrible accident. No one could believe it. One minute everyone at the wedding was joyous - the next it had turned into despair.
""To hear that two young children and their aunt had been killed on their way to the wedding was utterly heartbreaking. We were all numb, no one knew what to say. Some people actually left the wedding service to pay their respects - and others were in tears. It was one of the most harrowing things I've ever experienced. I am just so, so sorry.""