"I come with my two parents."
Translation:Ich komme mit meinen beiden Eltern.
It should be. The sentence does indeed ask for a translation for 'two' rather than 'both'. You are still correct. :)
Yes, that's wrong. But you can say ‘mit beiden meiner Eltern’ (with both OF my parents), with ‘meiner’ in the genitive.
It might be "meine" instead. I don't know if you have to inflect "mein" into the dative since you've already inflected beide, the word right before, into the dative. "Meine" would be nominative plural, matching Eltern.
Of course, you still produced the German "I come with both my parents" when asked to produce the German "I come with my two parents."