It was the first time in the history of the world championships that three siblings had all competed together in the same race. "It's great to have three brothers running," said Kevin Borlee. "We train together all year round. "We're three brothers who get on great, it is a special moment, be it as an athlete or for the family."

Jonathan did well to get back into third spot after a poor first leg from Gillet. Brazil's Wagner Cardoso then overtook debutant Dylan on his third leg to push the Belgian quartet back into fourth, but Kevin produced a strong anchor-leg to get back into third spot, with the top two of the three heats automatically qualifying along with the next two fastest.

The Belgians, who had finished fifth at the 2011 world champs in Daegu and one place lower at the 2012 Olympic Games in London, eventually finished third in their heat in a season's best of 3min 00.81sec.

The Belgian brothers, whose older sister Olivia won Olympic silver in 2008 and world bronze in 2007 in the 4x100m relay, lived to fight another day as they sealed one of the two fastest losers spots, along with Brazil.

The final of the 4x400m relay will take place on Friday, with the United States, Jamaica, Trinidad and Tobago and Britain among the favourites for the podium. "It's my first championships and it's really something else, it went so quick," added Dylan. "It's not easy but we qualified, that was our goal. Our time was good and we can go faster tomorrow."

First-leg runner Gillet said he was happy to be considered a "fourth brother". "It's never happened before in history, that's pretty cool," he said. "I've been running with Jonathan and Kevin for 10 years, and it's great." (AFP)