sibling
/ˈsɪbˌlɪŋ/Definitions
1. noun
A brother, sister, or other member of the same family
“She has two siblings, a brother and a sister.”
2. verb
To have or be a sibling
“They are siblings by marriage.”
3. noun
Brother or sister, especially when considered as a social or cultural unit
“In many cultures, the sibling relationship is highly valued.”