Chelsea have confirmed the signing of Thorgan Hazard, younger brother of Belgium international Eden, from FC Lens.
The 19-year-old, who has represented his country at numerous levels up to the Under-19 side, is not yet regarded as ready for the first-team squad at Stamford Bridge.
Hazard will become a member of the Blues' Under-21 side and could immediately be shipped out on loan to garner greater first-team experience.
Chelsea did not disclose details of the deal for Hazard, who has been with Lens since the age of 14, but only made his first-team debut for the Ligue 2 club last season.
A statement on the club's official website read: "He will now join our Under-21 squad, managed by Dermot Drummy, to continue his pre-season training and a loan move is being considered to continue his development."
The younger Hazard brother is regarded as a player with a similar style to his sibling, with the duo having played together previously for Tubize in their homeland.
Meanwhile, a trio of Chelsea youngsters will spend the season on loan away from West London, with forward Ulises Davila joining Sabadell in Spain's second division, while striker Milan Lakovic and goalkeeper Matej Delac will spend the campaign in Portugal's top flight with Guimaraes.