Cardiff Rugby can confirm Dillon Lewis and Jarrod Evans will leave the club at the end of the season.
The duo came through the club’s pathway together, playing for the Under-16s North, Under-16s combined and Under-18s before breaking into the first team squad.
Lewis has gone on to play 88 times for the Blue and Blacks and has also established himself as an international, winning 50 caps for Wales.
Evans has also graced the Test arena with Wales and has made 126 appearances for Cardiff racking up 765 points, which puts him second in the point-scoring list from the regional era.
Cardiff director of rugby Dai Young said: “It is always disappointing to lose quality players but the current situation in Wales meant we were unable to table competitive offers.
“They have contributed a huge amount during their time at Cardiff Arms Park and can look back on this chapter of their careers with pride. We wish them both all the very best for the future.
“We are now working hard to replace them and we hope to begin making some announcements soon.”
Lewis, who made his first team debut against Wasps during the 2014-15 season but it was in 2017 that he enjoyed his breakthrough.
He won his first Wales cap during that season’s summer squad and was part of Cardiff’s 2018 European Challenge Cup winning squad.
He said: “I am really grateful to Cardiff for everything they have done for me. They gave me the opportunity to become a professional rugby player and I have had a brilliant time over the past nine seasons.
“It is a club very close to my heart, I came right through the pathway with a lot of mates and made many more great friends along the way.
“I will miss pulling on the blue and black jersey and running out at the Arms Park but my priority was on securing my future and I am now excited for the next chapter in my career.
“Harlequins are another great club and I believe a new challenge and change of environment will be beneficial to my game.
"I remain committed to Cardiff for the remainder of the season and I’m thankful to everyone who has helped and supported me during my time here.”
Evans also enjoyed his breakthrough during the 2017-18 season and played a key role in the club’s Challenge Cup title for which he was named the club’s Discovery of the Year and Players’ Player of the Year.
He has featured 19 times this season and missed last weekend’s trip to Treviso due to injury.
Evans added: “I’m looking forward to joining Harlequins but I will always be very grateful to Cardiff.
“I have had a great time at the club and it has been an honour to pull on that famous number 10 jersey. Winning the Challenge Cup is an obvious highlight but there are so many other memories I will always cherish.
“I will miss the Arms Park and I am very grateful to the club, Peter Thomas, and all of the supporters.
“Given the situation in Wales, joining Harlequins was an opportunity I could not turn down and I’m excited to make the move in the summer but the focus right now is getting back on the pitch and helping Cardiff to a big finish to the season.”