First cousins are the children of your parents' siblings. For example, if your mother has a brother, his children are your first cousins. They share a set of grandparents with you, which makes them part of your extended family. First cousins typically grow up together, sharing family gatherings and holidays. They often develop close relationships, playing together during childhood and supporting each other as they grow older. The bond between first cousins can be strong, as they share similar family backgrounds and experiences, making them an important part of each other's lives.