Brothers Andy and Jamie Murray will face each other for only the second time in their professional careers at the Cincinnati Masters on Friday.
Andy and Feliciano Lopez beat Ryan Harrison and Jack Sock 2-6 6-3 10-7 to set up a quarter-final against Jamie and Neal Skupski.
Earlier, Jamie Murray and fellow Briton Skupski beat French pair Nicolas Mahut and Pierre-Hugues Herbert 6-3 6-3.
"I'd obviously rather be on the same side of the net as him," Andy said.
"It sucks, it's not ideal, but we'll still be brothers at the end of the match - providing nothing untoward happens," the Scot told BBC Sport.
Their only other meeting was in Montreal in 2015, where Jamie and John Peers beat Andy and Leander Paes in straight sets.
"I have ambitions to get back on the singles court as well, and doubles is Jamie's career, so it's hard in that respect. But you also have the professional obligation to go out there and give your best effort and try and win against your brother," Andy added.
The brothers could heed Serena Williams' advice - she has played her sister Venus 30 times, and at Wimbledon told Andy to "literally look at the ground - don't look at him at all".
"I don't think you're ever really ready to go compete against your brother," Jamie said after he and Skupski defeated the fifth-seeded Australian Open champions Mahut and Herbert.
"But it's just something that we'll both have to deal with. It's not an easy thing to have to go through, but it's only an hour and a half of our lives, so we can get through it I think.
"It is weird to look across the net and see your brother because you want each other to win every time they step on the court. And obviously you're getting out there and affecting what he's doing, and whether he's going to win or lose.
"It's not a natural thing to do, I would say, but it's just the nature of our sport."
Jamie's partner Skupski faced his brother Ken in World Team Tennis last month, and says he felt "weird playing against him".
Andy and Jamie frequently played singles against each other as juniors, and at times sibling rivalry boiled over.
Andy claims the nail on his left ring finger has never been the same since Jamie, tired of being taunted by his victorious younger brother, thumped him on the journey home.
"We were coming back from Solihull in the minibus," Andy told BBC Sport in 2015.
"I'd beaten Jamie in the final, I think, of the Under 12s so basically I was winding him up about that and my hand was on the hand rest.
"We were sitting next to each other and he just basically punched me on the hand - I lost my fingernail, and I've still got the scars to show for it."
The Murray brothers played together at the Washington Open earlier in August, losing in the quarter-finals.
Three-time Grand Slam winner Andy, 32, and Spanish partner Lopez were crowned champions at Queen's Club in June and beat fourth seeds Jean-Julien Rojer and Horia Tecau in the first round in Cincinnati.
The two-time Wimbledon champion made his singles comeback from hip surgery in Cincinnati on Monday, losing to Richard Gasquet.