Turkish word order - “Türkçe söz dizimi.”
Subject / time expression / place expression / object / verb.
The definite direct object can move anywhere before the verb. It is recognised by the accusative case suffix.
The indefinite, direct object in the nominative case always goes immediately before the verb.
"Yönetmen onun babasıdır." Translation: His father is the director.
What makes it not "the director is her father"?
"The director is her father." - Yönetmen onun babasıdır. - Correct.
His father is a director → Onun babası yönetmen(dir).
The current Turkish sentence is: "Yönetmen onun babasıdır." ("Director", that would be his father.) Placing it at the beginning sort of stresses it. Paraphrasing is one of our little tricks to circumvent the problem of "absence of a linguistic 'the'". Perhaps in 200 years, Turkish will develop a "the", but for now, we should make do with paraphrasing. :)
Just to clarify for those who are shaky on syntax: "director" here is not an accusative; it is a predicate nominative indicating that "director" and "his father" are the same person.
And as Ektoraskan said above, placing Yönetmen at the beginning of the sentence emphasizes it. More like "The director is his father" than "his father is the director". I used the first wording and it was accepted.