Andy Murray and older brother Jamie will become the first brothers to simultaneously occupy world number one spot when the year-end rankings are released on Monday.
Murray junior beat Novak Djokovic in the ATP World Tour Finals showdown on Sunday to retain his position on top of the ATP rankings charts.
It was a career-best 24th straight victory for the Scot and capped a fine year in which he won a second Wimbledon crown and defended his Olympic title in Rio.
He followed those triumphs by becoming the first Brit to clinch world number one spot with his eighth title of the season in Paris earlier this month to set up a thrilling season-ending tournament in London.
Djokovic knew he would have to better Murray's finish at the O2 Arena to wrest back a position he had held for 122 consecutive weeks prior to the Paris Masters, but defeat on Sunday ended the Serb's hopes.
ATP World Finals 2016 at O2 Arena - In pictures
Meanwhile, brother Jamie and partner Bruno Soares secured their place at the top of the doubles charts as French duo Pierre-Hugues Herbert and Nicolas Mahut were sent packing after defeat in their final round robin match on Friday.
Murray and Soares were subsequently defeated in their semi-final by South Africa's Raven Klaasen and American Rajeev Ram on Saturday, but it was bitter-sweet for the losing pair as they knew they could not be overtaken in the rankings.
After it became clear he and partner Soares would not be knocked off top spot, Murray said: "It's very exciting. It's a strange way to do it in the end but we've had a great year and won some big tournaments."
