Despite large amounts of care for chronic conditions being provided within the family, information regarding the extent to which siblings contribute to informal care practices in families where a child has a chronic condition is limited. This article draws on multiple perspective data from 24 families that had a child with epilepsy. In doing so, the article illustrates siblings' significant contribution to caring for their brother or sister and further develops the alert assistant concept. Two additional distinct caring roles that the siblings took on are also outlined – the substitute parent and parenting assistant roles. The relationship between siblings' socio‐demographic characteristics and their caring responsibilities is also explored. The paper's findings are that siblings who were older, female and those in families with a higher child to parent ratio took on more caring responsibilities. Consequently, this article contributes to the currently limited literature on siblings who care for a chronically ill brother or sister by increasing understandings of different caring roles and experiences of chronic illness in families.