England internationals Mako and Billy Vunipola have signed new four-year contracts with Saracens.
The brothers are now tied to the Gallagher Premiership champions until 2022.
Prop Mako, 27, joined Sarries from Bristol in 2011, with 25-year-old number eight Billy moving from Wasps two years later.
"It's pleasing to get the opportunity to play here at a great club where I've spent most of my adult years," Mako told saracens.com.
"We're very lucky a lot of us have grown up together and genuinely consider each other family.
"You can see that on the field but off it we love each other's company; it's a bit cringe sometimes but for me that's what makes this club so strong."
The duo have played a major role in Saracens' recent success, winning three Premiership titles and two European Cups in the past four years.
Mako has made 144 appearances for Sarries, while Billy has played 85 times.
They are the latest players to commit their futures to the club this summer following new deals for Brad Barritt, Juan Figallo, Vincent Koch, George Kruis and Duncan Taylor.
Billy added: "I'm very happy to be staying here. It was a straightforward decision; it was always about how I enjoyed being around the club and the boys.
"I'm looking forward to growing as a group and growing friendships I already have.
"A lot of the boys who have been here for a long time have already re-signed like Brad, Kruiso and Duncan - the coaches too.
"I can't wait for the group to grow more and it's something that excites me."
England player of the year Mako has won 51 international caps and was also a member of the British and Irish Lions squads which toured in 2013 and 2017, while Billy has represented his country 36 times.
Saracens director of rugby Mark McCall said: "Mako and Billy have both made outstanding contributions to Saracens over a number of years.
"They've played a very significant role in the development of the group both on and off the field and naturally we're thrilled they've committed their future to the club for another four years."