The groom, Ben Smethurst, 26, said the fight began when his brother and best man, Danny, reached over a table for a piece of chicken.
Curt Hughes, the bride's uncle, yelled at the best man and then punched him, Smethurst said.
Hughes then punched the bride's sister, mother and father, the groom said.
The bride's sister, Krystel Coleman, was taken to the hospital with a broken nose and two black eyes, The Sun reported.
"I was out cold for about 20 minutes," Coleman said. "It was supposed to be my sister's special day and it was ruined at the end."
Eight cop cars and two police vans reported to the scene, and Hughes, 53, was arrested on suspicion of assault, The Sun reported.