Tuilagi brothers Alasea and Anitelea will return to the Aviva Premiership to join Newcastle this summer.
The Samoa internationals, both of whom play on the wing or at centre, have signed two-year contracts and become the Falcons' seventh and eighth new arrivals ahead of next season.
Alesana, who was a star of the Leicester side which won three Premiership titles between 2007 and 2010, will join from Japanese club NTT Shining Arcs while younger brother Anitelea will leave Newport-Gwent Dragons for Kingston Park.
"I'm extremely excited at the prospect of returning to the Aviva Premiership with Newcastle," said Alesana.
"Newcastle is a big club with huge potential, and under Dean Richards there is an exciting vision for rugby in the North East which I want to be a part of.
"I really enjoyed my time in the Premiership with Leicester, and I'm delighted to get the opportunity to play in what I see as the most competitive league in the world."
Anitelea, who also played for Leicester, said: "There are certainly big things taking shape at Newcastle and it's a club that is looking to thrive in the Premiership next season.
"I can't wait to get stuck into pre-season now with my new teammates."
Newcastle boss Dean Richards said: "Andy and Alex are quality acquisitions and have bags of experience at the very highest level.
"I'm delighted that we have secured their services for next season, both of whom will undoubtedly add some real firepower to our backline."