Alistair and Jonathan Brownlee are among the World's elite in the sport
The Brownlee brothers have dominated the sport of triathlon in recent years, but they still look out for each other on the course.
In the last two Olympic Games, Alistair has won back-to-back gold medals, while younger brother Jonathan won silver in Rio de Janeiro, to improve on the bronze won at London 2012.
Sunday saw the end of the Paralympic season, with the final race of the World Series taking place in Cozumel, Mexico. Jonathan needed to win the race to win the overall World Series, and was leading inside the last kilometre when he began to visibly struggle.
Alistair, who was in third place at the time, helped his brother to the finish, before eventually pushing Jonathan over the line into second place after South Africa's Henri Schoeman won the race.
Jonathan's second place finish, was originally under the judge's review due to his brother's assistance, but was eventually confirmed. The World Series was won by Spain's Mario Mola.
After the race, Alistair told the BBC that he would have done the same, if it was any other athlete, and not just his brother. He called it "a natural human reaction".
The younger Brownlee was brought to hospital after the race, but took to social media, to show he was only badly dehydrated, with no long-lasting damage.