Jamie and Andy Murray's successful doubles partnership was instrumental in Great Britain's Davis Cup win in 2015
Andy and Jamie Murray lost in three sets to Raven Klaasen and Michael Venus in the quarter-finals of the Washington Open.
The British pair took the first set on a tie-break but lost a second as all 24 games followed serve.
South African Klaasen and New Zealand's Venus, seeded third, trailed 5-7 in the final tie-break but won five points in a row to win 6-7 (3-7) 7-6 (8-6) 10-7.
Andy Murray, 32, is playing his fourth event since hip surgery in January.
The former world number one feared his career might be over before having the hip resurfacing operation, but returned to the doubles court five months later when he won the Queen's title alongside Spain's Feliciano Lopez.
The three-time Grand Slam winner says he could make a singles return at the Cincinnati Masters later this month - two weeks before the start of the US Open in New York - and has been practising singles play this week.
"I feel fine, just disappointed," Murray said of his fitness after the defeat. "Practices have been fine.
"Just keep pressing next 10 days. If I feel ready, I'll give it [singles in Cincinnati] a go. If not, I'll probably wait until after New York."
The Murray brothers, who were playing in doubles competition together for the first time since 2016, reached the Washington quarters after a gutsy three-set win over experienced French pair Nicolas Mahut and Edouard Roger-Vasselin in their opening match.