Mako and Billy Vunipola have signed new contracts with Premiership champions Saracens until 2019.
The England forwards have played key roles in the London club's success in recent years and the brothers have been rewarded with fresh deals.
Saracens director of rugby Mark McCall explained: "This is fantastic news for everyone associated with the club.
"To have two players of the calibre of Mako and Billy commit their futures to Saracens is extremely exciting, as we continue to build a strong squad for the upcoming seasons.
"We have a great blend of youth and experience at the club and what has been great is for us to witness the progression of both of them from promising youngsters to two of the world's best in their respective positions.
"They also contribution off the field is equally as important and we're delighted to keep them at the club."
Mako, 25, joined the Premiership leaders from Bristol in 2011 and his younger Billy, 23, made the move from Wasps three years ago.