The Dolphins continue to build their burgeoning young forward stocks by signing Newcastle giant Sebastian Su'a, son of a former New Zealand Test cricketer.

The 21-year-old prop, who stands at 198cm, is the progeny of 1990s Black Caps' left-arm paceman Murphy Su'a.

New Zealand-born Su'a, who has played just one NRL match, will join his former Knights front-rower Daniel Saifiti at the Dolphins in 2026 on a two-year deal.

AAP understands Saifiti, who joined the Dolphins in the off-season, rates the tyro highly and is looking forward to linking with his old teammate.

Saifiti is not the only Dolphin who regards Su'a as a prospect.

"Our assistant coach Rory Kostjasyn knows Sebastian from his time at the Knights and we believe he will have a really good opportunity to make an impact here," Dolphins' CEO Terry Reader said.

"Having someone of that size, learning from the experience of our existing pack, makes Seb an exciting prospect for us."

The Dolphins are preparing for the future by signing Su'a. Former skipper Jesse Bromwich, one of the great props of the modern era, retired at the end of last year.

Current front-rower Mark Nicholls (35) is in his twilight years while former Melbourne title-winning back-rowers Felise Kaufusi (32) and Kenny Bromwich (33) have transitioned into middle forwards

The Dolphins have signed or extended young gun forwards Max Plath (23) and Kulikefu Finefeuiaki (21) in recent months and Su'a is the next cab off the rank.

Su'a played his junior league with Mount Albert Lions and also was a promising rugby union player.

He joined the Knights in 2022 and progressed through the Jersey Flegg and NSW Cup competitions before debuting against South Sydney in round 25 last year.

He hails from a sporting family with father Murphy Su'a playing 13 Tests and 12 one-day internationals for New Zealand. He captured 36 Test wickets at an average of 38.25, including a career-best of 5-73 against Pakistan in 1993.