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 indeed looks redundant vs the English construction, but that is the rule.
there is another form to avoid redundancy: "quand est-ce que mes parents vous disaient ça ?" (pls note there is a T liaison between 'quand' and 'est-ce')
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
"Quand" should be said with a nasal sound and sounds more like "comment" here especially the slower version and both are equally likely to be said
Just lost a heart because they didn't accept "When did my relatives tell you this?", Marked "relatives" as wrong, even though that's in the possible translations.
In French, "mes parents" are Mom and Dad.
"parents" as "relatives" is without possessive adjective.
See the parallel with "la fille" = the girl and "ma fille" = my daughter