Raphael Cabral scored a trilogy for Portugal before Ronaldo Junior set out on the bench.
Ronaldo, 40 years old, scored 136 goals for Portugal, a record in men's football.
Portugal has made his first main title in Euro 2016 and the Nations League title in 2019.
Ronaldo Junior in Nasser, Saudi Arabia, with his father, who signed at the Professional League Club in 2022.
Ronaldo Sr Forward has four other children – Twins Eva and Mateo, 7, Alana Martina, 7, and Bella, 3.
Portugal U15s will play the Vlatko Markovic championship, where they will face Greece on Wednesday and England on Friday.
