Craig and Jamie Overton have agreed extensions to their Somerset contracts.
The 19-year-old twins, from Northam, have signed for another three years with the county.
Having gone through the Somerset Academy, while playing for Instow-based North Devon, the Overtons made their first-team debuts last year.
Both have played for England’s under-19 and Lions teams and fast bowler Jamie was in the full squad for the NatWest Series against Australia during the summer.
Dave Nosworthy, the Somerset director of cricket, said: “We are extremely pleased to have secured these two young diamonds.
“Both Craig and Jamie are very highly rated nationally and as West Country lads we are excited to be able help them develop and at the same time have them performing on the field for us.
“Long-term expectation around these two is high, so it will be key now for them to just keep their feet on the ground and get the hard yards in.”
Jamie played 13 first-class matches this year, taking 35 wickets at an average of 34.88. He also took 12 wickets at 31.41 in nine one-day matches.
He said: “Signing a new deal with Somerset is the cherry on top in terms of what has already happened for me this season. I look forward to a long association with the club, and to winning as much silverware along the way as possible.”
Having toured Australia with England Lions last winter, Craig seemed set for a big summer at Somerset but a stress fracture in his back ruled him out for the majority of the campaign.
He said: “It is an honour to have signed an extension with the club I have always supported and have always wanted to play for. It is an exciting time for me and I can’t wait to get back out on the field come the 2014 season.”