Search for flex assets by its parent name

I created a flex family with parents assets for categorizing my assets and included the parent definition in the asset type definition.

For example, the parent has a name attribute of value "x". when I search for asset with "x", the search result contains the parent asset only but I want also the children assets to be returned in the result.

Note: This behavior is working with FisrtSiteII and Avisports sample sites but doesn't work in my site.