So, in this context, the expressions means, 'if his parents had got what they wanted' i.e. if they had decided his career for him.
The expression repeats the word, 'had'. This is because the tense we are using is the 'past perfect' tense. In this tense, we use 'had' + the past participle of the verb. In this case, the verb is 'to have'.
In this sentence, the structure is part of a third conditional structure. We use this structure to speculate about the past or present result of an earlier event.