Identical twin sisters training a quinella might be one of the rarer things to happen on a racecourse.

Goulburn trainers Emma and Lucy Longmire could make it happen in Saturday's Highway Handicap at Randwick.

Emma has Thunder Road in the race, while Lucy will saddle up Percivale.

Emma says it's the third time she's been up against her sister, but there's no serious sibling rivalry.

"We support each other," Longmire said.

Thunder Road gives Emma the chance to train her first city winner, a milestone Lucy achieved in 2013.

The four-year-old gelding is known as Thunder The Wonder to connections, but at one stage Longmire was wondering whether he would make it as a racehorse.

"The owners bred him and they wanted to continue on with him," Longmire said.

It proved to be a wise choice when he ran a creditable fourth at Kembla Grange in the first start of his last preparation.

"The day he ran fourth at Kembla you could have heard us all from the other side of the track," Longmire said.

"We were roaring down the grandstand."

That preparation ended with a maiden win at Moruya at his fourth start in February, giving Thunder Road his ticket to begin his next campaign at Randwick where the roar could return if he can pull off an upset.

"He's a very unassuming horse," Longmire said.

"He's not overly talented but he does go on a wet track and he tries - that's half the battle."

Percivale will be having his second start after a long break with his two wins over 2006 and 2300 metres.

The 1400m of Saturday's race doesn't worry Longmire with Thunder Road and she is happy if a heavy track makes it a tough slog.

And the prospect of a Longmire twins quinella?

"That'd be lovely," Longmire said.