Sibling

thumb|Identical twins can be difficult to visually distinguish especially when young, as demonstrated by brothers Billy and Bobby Mauch. Twins are two offspring produced by the same pregnancy. Twins can be either monozygotic ('identical'), meaning that they develop from one zygote, which splits and forms two embryos, or dizygotic ('non-identical' or 'fraternal'), meaning that each twin develops from a separate egg and each egg is fertilized by its own sperm cell. Since identical twins develop from one zygote, they will share the same sex, while fraternal twins may or may not. In very rare cas

A sibling is a relative that shares at least one parent with the other person. A male sibling is a brother, and a female sibling is a sister. A person with no siblings is an only child.

thumb|American band Jackson 5: Tito, Marlon, Michael, Jackie and Jermaine Jackson

ordered list of individuals in line to take on a given position should the office become vacant

child of a sibling or half-sibling

bed in which one bed frame is stacked on top of another

culmination of one multiple pregnancy, wherein the mother delivers two or more offspring; applicable to placental species

child without siblings

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The avunculate, sometimes called avunculism or avuncularism, is any social institution where a special relationship exists between an uncle and his sisters' children. This relationship can be formal or informal, depending on the society. Early anthropological research focused on the association between the avunculate and matrilineal descent, while later research has expanded to consider the avunculate in general society.

psychological hypothesis

holiday honouring relationships of siblings

effect that the more older brothers a male has from the same mother, the greater the probability he will have a homosexual orientation

sequence in which children are born into a family

facility which stores umbilical cord blood for future use

physical, emotional, and/or sexual abuse of one sibling by another

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type of competition or animosity among siblings

a child who is conceived in order to provide an organ or cell transplant to a sibling that is affected with a disease

theory on birth order of siblings