Which event tends to cause an increase in sibling contact and support during middle adulthood?

The event that tends to cause an increase in sibling contact and support during middle adulthood is often the onset of aging-related issues or health crises in parents. As siblings come together to provide care or support for their aging parents, they frequently strengthen their own relationships. Additionally, life transitions such as children leaving home or the loss of a parent can prompt siblings to reconnect and offer emotional and practical support to one another.