Translation:When did my parents tell you that?
'ils' means 'they'. The phrase 'ils disaient' (they said) is inverted here, because the sentence is a question, to form 'disaient-ils'. 'Vous' placed before the verb ('disaient') means 'to you'. 'Ça' means that. So piecing it all together LITERALLY makes "when my parents to you said-they that?', or 'when did my parents tell you that?
It's often used for emphasis, to make sure he knows about MY PARENTS saying things... http://french.about.com/od/pronunciation/a/tonicaccent.htm