Sibling

"A sibling is a gender neutral word for a relative that shares at least one parent with the subject. A male sibling is a brother and a female sibling is a sister. If a relative has no siblings, it is an only child.

In most societies throughout the world, siblings often grow up together, thereby facilitating the development of strong emotional bonds. Sometimes, they may grow up apart in foster care. The emotional bond between siblings is often complicated and is influenced by factors such as parental treatment, birth order, personality, and personal experiences outside the family.

Medically, a full sibling is a first-degree relative and a half sibling is a second-degree relative as they are related by 50% and 25% respectively." - (en.wikipedia.org 06.01.2021)