"They are not visiting their parents."
Translation:Oni nie odwiedzają ich rodziców.
Is the 'ich' necessary here? I wonder because it wasn't so in a previous question in this lesson.
It shouldn't be necessary. Also, "swoich" is a lot more probable than "ich". But it hasn't been introduced yet at this point in this course.
"swoich" would mean that it's about their own parents.
"ich" is... well, about some other "their" parents.
Added the option to not use any possessive, it's natural and it will be understood that it's about their own parents.