Born in Purmerend in the province of North Holland on 11 January 2008, Sean began his footballing career at RKAV Volendam, joining the club as a six-year-old.
Two years later, Sean moved to Ajax's famous youth academy which has produced many Dutch greats such as Johan Cruyff, Clarence Seedorf, Dennis Bergkamp and Patrick Kluivert, with the latter scoring 13 goals in 37 appearances for Newcastle.
After progressing through Ajax's youth ranks, making his professional debut in May 2024 for the club's reserve team Jong Ajax, Sean signed his first professional contract with the Dutch giants on a three-year contract.
During the 2024/25 season, he began training with the first team before making his Eredivisie debut in February 2025, appearing in the closing stages of a 4-0 win against Heracles Almelo.
Sean's development continued into the following season as the teenage Dutchman enjoyed a breakthrough campaign at senior level last term after making 25 appearances, including 18 starts.
The central midfielder, standing 6ft tall, gained praise following Ajax's 1-1 draw in De Klassieker against rivals Feyenoord in March, scoring his first Dutch top-flight goal at the age of 17.
He also made his full UEFA Champions League debut with Ajax in December's 4-2 away win against Qarabağ FK, becoming the club's youngest ever player to provide an assist in the competition.
That season, Sean was the recipient of the Abdelhak Nouri Trophy – Ajax’s annual award for the club’s brightest academy talent. Previous winners include the likes of Ryan Gravenberch, Christian Eriksen, Wesley Sneijder and Rafael van der Vaart.
Sean has represented his country throughout a number of age groups, ranging from under-15 to under-19 level.
After making his under-18s debut in September's 2-1 friendly win against the United States, Sean scored twice in six appearances before making his under-19s bow in March during a European U19 Championship qualifier against Finland.
Sean becomes the Magpies' third signing of this summer's transfer window following Ewen Jaouen and Bazoumana Touré's arrivals from Stade de Reims and TSG Hoffenheim respectively.
The 18-year-old is excited at the prospect of playing for "a giant club in the Premier League" as well as competing in "the best league in the world".
Sean said: “I was at home at Ajax – I joined when I was seven and I leave with only good memories, but when a club like Newcastle comes for you, it’s really hard to say no. The last few days have gone fast and I’m very happy to join.
“I’m a player who likes to get on the ball and play forward all the time. I’m happy playing between the lines and I feel I have a lot of energy in my game. I just want to win.”
