Juan Carlos Familia-Castillo (born 13 January 2000) is a Dutch professional footballer who plays as a left back for RKC Waalwijk.

He scored twice in a 4–2 win against Atlético Madrid in the group stage, converted his kick in the penalty shoot-out by which they beat Porto U19 in the semi-final,[7][13] and played at left wing-back in the final, a 3–0 defeat to Barcelona.

[15][16] Facing Porto in the final, he crossed for Daishawn Redan's header that tied the scores soon after half-time,[17] and according to the football.london website, "showed a lot of energy and was probably the most threatening player for Chelsea" in the second half, but they lost 3–1.

[18] Promoted to the under-23 team, Castillo made his debut in open-age football in August 2017, as a 74th-minute replacement for Cole Dasilva in the 2017–18 EFL Trophy against Plymouth Argyle, who won the match on penalties.

[2] He made his senior debut in the Eerste Divisie on 13 September, playing the whole match at left back as Jong Ajax let slip a 2–0 lead away to De Graafschap and lost 3–2.

[27] Castillo had to wait until 27 December – the last match before the winter break – to make his debut for AZ, as an 89th-minute substitute in a 2–2 draw with FC Utrecht.

[7][32] Castillo signed a one–year contract extension with Chelsea and then, on 6 July 2021, joined EFL Championship club Birmingham City on loan for the 2021–22 season.

[35] He started in Birmingham's two EFL Cup ties, but his next appearance was not for a further three months,[7] when he came on at right back with 25 minutes left of the visit to league leaders Coventry City "showing energy and the physical grit to throw himself into tackles" to help the side achieve a goalless draw.

[46] He was a member of the squad for the championship finals in Croatia, and played in all four of their matches as they finished second in their group before being eliminated at the quarter-final stage by Germany U17.