public PageReference ParentLink { get; set; }

Parent and childhood is determined by placement in the Web page tree.

In the following code example ParentLink is used twice. Firstly to make sure it contains a non-empty PageReference and secondly to retrieve the sibling of the current page.

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if ( CurrentPage.ParentLink != EPiServer.Core.PageReference.EmptyReference ) 
{
    EPiServer.Core.PageDataCollection siblings = GetChildren( CurrentPage.ParentLink );
}

The following code example demonstrates the usage of ParentLink. The example results in the name of the parent page being displayed.

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Parent Page Name: <%= GetPage( CurrentPage.ParentLink ).PageName %>