Newcastle's Jesse Southwell has been cleared to play NRLW and will join her older sister at the Knights in 2022.
Fresh from claiming a rugby sevens gold medal at the Commonwealth Games in Birmingham, the 17-year-old from Cameron Park could potentially make her debut in the senior ranks as early as next weekend's opening round.
The Knights officially announced her signing on Wednesday morning.
Southwell needed dispensation to play NRLW because of her age, with 18 the normal requirement.
Southwell's sibling Hannah - an NRLW premiership winner, NSW regular and Jillaroos representative - was recruited by her hometown club this year after several campaigns with the Sydney Roosters.
The Knights, who have now completed their 24-player roster, are set to embark on their second NRLW season.