Uncapped brothers Niall and Rory Scannell have fought their way into Ireland's 40-man RBS 6 Nations squad thanks to a string of impressive performances with Munster.
Hooker Niall Scannell will compete with Leinster's James Tracy to understudy captain Rory Best, while Rory Scannell adds depth in the centres.
Head coach Joe Schmidt has named three uncapped players in all, with Munster's Andrew Conway completing the new additions.
Linchpin fly-half Johnny Sexton is included as expected despite battling a calf complaint, while Niall Scannell's addition offsets the loss of Sean Cronin and brother Rory boosts the midfield with Jared Payne missing through a long-term kidney problem.
"It has been good to watch the players over the past two months and great to see many of them doing so well," said Ireland boss Schmidt.
"As always there were some difficult decisions but we feel that the group is a good mix with a number of key players having good experience and a number of newer players having gained valuable experience and confidence during the summer tour to South Africa and the recent autumn series."
Hooker Niall Scannell has been rewarded for his fine Munster form this term, the 24-year-old starring as the Thomond Park province secured a home quarter-final in the European Champions Cup.
Ireland will feel the loss of the hugely-experienced Cronin as robust back-up to captain Best, but have confidence that the form of both Niall Scannell and Leinster's Tracy can fill that void.
British and Irish Lions playmaker Sexton hobbled out of Leinster's 24-24 draw at Castres on Friday night, but his withdrawal is hoped to have been little more than precautionary.
Ireland start their Six Nations campaign by travelling to Murrayfield to face Scotland on Saturday, February 4, and hope by that time to have Sexton back to full fitness.
Ulster's Paddy Jackson remains the main understudy to Sexton, with Leinster's fast-improving youngster Joey Carbery sidelined after ankle surgery.
Stuart Olding misses out with injury in the centres, handing his Ulster colleague Stuart McCloskey a recall.
Ireland's 40-man squad for the first two rounds of the RBS 6 Nations Championship:
Forwards: F Bealham (Connacht), R Best (Ulster, capt), J Conan (Leinster), U Dillane (Connacht), T Furlong, C Healy, J Heaslip (all Leinster), I Henderson (Ulster), B Holland, D Kilcoyne (both Munster), D Leavy, J McGrath, S O'Brien (all Leinster), T O'Donnell, P O'Mahony, D Ryan, J Ryan, N Scannnell, CJ Stander (all Munster), D Toner, J Tracy, J Van der Flier (all Leinster).
Backs: T Bowe (Ulster), A Conway, K Earls (both Munster), C Gilroy (Ulster), R Henshaw (Leinster), P Jackson (Ulster), R Kearney (Leinster), K Marmion (Connacht), L Marshall, S McCloskey (both Ulster), L McGrath (Leinster), C Murray (Munster), T O'Halloran (Connacht), G Ringrose (Leinster), R Scannell (Munster), J Sexton (Leinster), A Trimble (Ulster), S Zebo (Munster).
Choosing a captain is always an important decision as a head coach. Captains are the conduit for a coach’s philosophy, a sounding board, an intermediary between the coaching staff and the players. They are the rallying point. They set the tone on and off the pitch.