noun
parents and siblings; one's immediate family
Refers to one's parents and brothers/sisters collectively; can also extend to close relatives in a broader sense.
親兄弟に心配をかけてはいけない。
You mustn't worry your parents and siblings.
親兄弟の助けがなければ、ここまで来られなかった
Without the help of my family, I couldn't have come this far.