Berdel or "sibling swapping" is a type of marriage where parallel families swap siblings. It does not always have to be a sibling, and sometimes another family members is swapped in exchange for another family member. For example a niece can be exchanged for a parallel family's cousin etc. Sometimes, if the family member swapping is arranged by a family matriarch or patriarch, it is viewed as narcissistic. However if berdel is arranged by a similar aged relative, those marriages are often seen as very safe, and even as a marriage where the well-being is guaranteed through the insurance of the counterpart swapped relative. The reason why berdel marriages or sibling swapping marriages are safer is because the two families already trusted each other before.