Kit Connor and Joe Locke in the Netflix coming-of-age series "Heartstopper," whose third season premiered last week. Samuel Dore/Netflix

You can’t choose what happens to the people you love, or the choices they’ll make, or how their past trauma will impact their present lives. These are tough relationship lessons, lessons that you wouldn’t expect a teen TV show to explore. That’s what sets Netflix’s “Heartstopper” apart from its coming-of-age contemporaries.