Yes you are.
As a 17yr old I was routinely out past 10:30. I had a job. Maybe this girl and her brother did too? But that doesn’t occur to you.
But even so... That’s just not late for a 17yr old even just merely out for fun with friends, or in this case, a brother. That’s pretty common even just going to a movie.
I really don't understand the logic of your post. I don't know about your 11 pm job or your brother or whatever. My son has proven himself responsible, he was home by 10:30 (just like these kids). He just wanted to experience the joy of driving a car without his mother in the passenger seat, as I had been for the last two years. I also taught him to drive a stick shift. If that is negligence, then you are a control freak.