Sibling/'sɪblɪŋ/ - a brother or sister
Когда siblings за что-то борятся, используем слово rivalry/'raɪvəlri/ (аналог competition).
Sibling rivalry is the jealousy, competition and fighting between brothers and sisters.
Например, борьба за шоколадку: there is rivalry for the bar of 🍫
As for me, I have a younger sister. She was the one who got me hooked on (подсадила) anime and manga 😊
Do you have siblings?