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