You could say "los niños son jóvenes".
You say, "gemelos."
You can say los chicos for the boys, and las chicas for the girls.
Nothing, that's in English. But if you meant to say HOW to say teenage boys, then its "adolescentes"
hola chicos
Odio los chicos.
acelerado for boys and acelerada for girls
me gustan los chicos
Nuestros muchachos. (Chicos, niños.)
girls, debriefia and boys, debriefio
i feel young = me siento joven
Girl who are friends are amigas in spanish. Further boys are amigos
'Young people' in Spanish is 'los jóvenes'