SPListItem.FirstUniqueAncestorSecurableObject property
SharePoint 2013
Retrieves the first unique ancestor if it has unique role assignments otherwise returns the first parent object (folder, list, or Web site) that has unique role assignments.
Assembly: Microsoft.SharePoint (in Microsoft.SharePoint.dll)
Property value
Type: Microsoft.SharePoint.SPSecurableObjectA SPSecurableObject that represents the first unique ancestor of this [Microsoft.SharePoint.SPListItem] object.