A brother or sister. (Cambridge Dictionary)
Your siblings are your brothers and sisters. (Collins Dictionary)
One of two or more individuals having one common parent. (Merriam – Webster)
One of two or more things related by a common tie or characteristic. (Merriam – Webster)
From a federal judge to an alcoholic who died at age 43: Meet Donald Trump’s siblings.
7 Ways Parents Can Address Sibling Bullying.
3 Steps that Transform Sibling Conflict into Sibling Camaraderie.