His parents didn't want him to go. This is how I would write it, but when trying to translate it (to swedish) it seems he would be the correct word to use. I would never have thought twice about using him if it wasn't for the fact I have to explain why him not he. Please help me out!
His parents didn't want him /* he to go.
"He" is impossible her. The pronoun is the syntactic object of the verb "want", and hence takes accusative case "him".
The pronoun is also the understood subject of the subordinate clause "to go", and pronoun subjects of infinitival clauses always take accusative form.
His parents didn't want him to go.
This sentence is correct. "him" in this sentence is the object.
If you use "he", it will be incorrect since the word "he" must only be used as the subject of a sentence. Let me give you some examples that are similar to this.
Her parents didn't want her to go.
My parents didn't want me to go.
Our parents didn't want us to go.
Their parents didn't want them to go.
Your parents didn't want you to go.
Therefore, the translation that you translate that sentence in English into Swedish might be wrong.