Residents in the town of Sanban said the three brothers had been waiting for their brides' party to arrive when the missile hit their house.
The airstrike hit wedding tents in which women and children had gathered separately from men. As many as 135 people were reportedly killed.
The Saudi-led coalition denied responsibility for the incident, which is believed to be the deadliest attack yet on civilians in Yemen's ongoing war.
The incident occurred just hours before Afghan forces took control of the country's security at the conclusion of the joint US-NATO mission.