Coleraine rower Peter Chambers will join his brother Richard in the British lightweight four boat at the Olympics.
After helping Britain take second at this season's opening World Cup meeting in Belgrade, Peter Chambers was ruled out of the Lucerne regatta by injury.
Paul Mattick was his replacement in Switzerland as the British finished behind China and South Africa.
Another Coleraine rower Alan Campbell will compete for Britain in the single scull in London.
Campbell won world championship bronze last year but finished a disappointing fourth in Lucerne nine days ago behind Ondrej Synek, Mahe Drysdale and Cuban Angel Fournier Rodriguez.
Peter Chambers has been drafted into the lightweight four boat this season after winning world titles at Under-23 and senior level in the non-Olympic class lightweight men's pair last year with Newcastle's Kieren Emery.