The sister duo looking to steer the Steelers to Tarsha Gale Cup glory

Sister act Sienna and Rhian will line up for the Steelers at CommBank Stadium in Parramatta in what will be an emotional decider against the Knights.

The Steelers Tarsha Gale Cup side has so far been invincible, going the entire regular season without defeat and then going on to dismantle the Sharks 26-4 in the semi-final.

18-year-old lock Sienna is in her second season in the U19's while 17-year-old utility Rhian joined her after moving up from the all-conquering Lisa Fiaola Cup Development squad.

Both are hoping to graduate to the Steelers Harvey Norman Women's Premiership team on completion of the U19s competition, joining cousin Zali, the sister of Panthers NRL lock Isaah.

But the sister duo aren't thinking any further ahead than their game on Saturday, April 27 in Parramatta.

"I enjoy playing with my younger sister, she is a ball of energy," eldest Sienna said.

"I feel like we do have our conflicts off the field, but when we get on the field, we're best friends. I feel like we just connect on the field. When we're on the field together there's a smile on my face just having my sister alongside me.

"I feel like if we win the grand final then there will be tears in my eye. So having her along this journey is an unreal experience. I just can't believe it's happening.

"If you told me this five years ago, I wouldn't have believed you. It's pretty amazing."

Meanwhile for younger sister Rhian, playing in a grand final alongside her older sister was a dream come true.

"I think sharing things with the family is probably the best thing to do," Rhian said.

"You don't understand it until you play with your siblings. It's pretty special to win a grand final with you family. Dad really loves us in the same team. He will be stoked and the whole family will be stoked."

Not much has stood in the way of Courtney Crawford's side this season, but a late arrival to the semi against the Sharks threatened to do so.

It was a rushed preparation into the match, with a late bus meaning the team only arrived at Leichhardt Oval 30 minutes prior to kick-off.

"We all gelled as a team," Sienna said.

"We were meant to get there early to cheer on the Lisa Fiaola girls at 12. We had a very rushed preparation from getting off the bus to actually taking the field to warm up.

"But I feel like we took away everything and to play how we played on the day against the Sharks, I just think all the girls were pretty happy. We've been playing all season together so we didn't change anything. We just kept it easy for ourselves."

Just one more game stands in the way of the Steelers completing an unbeaten season in the Tarsha Gale Cup. But they are under no illusions of the battle they will be up against.

"I'm expecting a challenge from them," Rhian said.

"They will definitely come out hard in the first 15 minutes to try and sway our confidence. As long as we stay confident, I back out girls. We've worked hard all season for it. Every single one deserves the victory."

Kickoff for the match on Saturday will be at 1:30pm and will be live streamed on NSWRL TV.