Kaufusi has signed for next season with the option of an additional year while Welch has put pen to paper on a new two-year deal to remain in Melbourne.
The re-signing of the young props is yet another significant boost for Storm’s forward pack.
Kaufusi and Welch join teammates Dale Finucane, Joe Stimson and Jesse and Kenny Bromwich as the latest big men to re-sign with Storm.
Welch, 22, has played 33 games in the purple jersey including last year’s NRL Grand Final.
Over the last two years his aggressive style of play has proved a real asset for Melbourne.
This season has seen Kaufusi break into Craig Bellamy’s starting side.
The 24-year-old Tongan international has played every minute, of every game this season, taking his opportunity in the second row with both hands.