You guessed it, Norwegian director Joachim Trier (b. Denmark, 1974) is related to that other great Scandinavian film-maker. Jacob Trier, who was the sound technician of Norway's most popular film ever "Pinchcliffe Grand Prix," as well as "Virgins of Riga" (among others).
Oh, not who you were thinking of? Wow, you know your Norsky cinema! Joachim is also the grandson of the important Norwegian film maker Erik Løchen, director of Motforestilling (1972) and The Chasers (1959).
Still not the right Trier? Assuming you're not thinking of Joachim's mother (Mrs. Trier), I guess you might be thinking of Lars von Trier, to whom he is also distantly related. Lars added "von" just because he thought it sounded more film-maker-ish. Which I suppose it does. It's certainly better rhythmically; "Lars Trier" is just too abrupt, peremptory almost. Two stressed syllables, back to back like that, it just doesn't work. What was his mother thinking? No wonder he's such an unpleasant man. You get that unstressed syllable in the middle there, it's at least more euphonious. And takes up a bit more space, if you know what I mean. Which must be somewhat reassuring to poor Lars. And to his distant cousin, Joachim, not to mention Jacob and Erik and Erik's wife.