sibling

Do you have any siblings? [=brothers or sisters]你有兄弟姐妹吗？

younger/older siblings弟弟妹妹；哥哥姐姐

sibling relationships兄弟姐妹关系

There was barely any sibling rivalry [=competition between brothers and sisters] in our family.我们家兄弟姐妹间几乎没有竞争。