The Boys from Brazil (1978) on Netflix

A young aspiring Nazi hunter is in Paraguay keeping an eye on Josef Mengele, a Nazi doctor who performed experiments on Jews during the war. The man has been calling famed Nazi hunter, Ezra Lieberman and Lieberman is annoyed by his calls. When Mengele has some guests he decides to bug his meeting. Just when he was about to get some details, Mengele finds the bug. So he runs off and calls Liberman and tells him that Mengele is planning to kill 96 men who are 65 years old all over the world. Just as he was going to tell Liberman more, Mengele finds him and kills him. Liberman receives some photos he sent of Mengele's guests, he recognizes some of them as Nazis so he decides to keep an eye out for a rash death of 65 year old men. Mengele upon learning of Liberman's snooping wants him killed but his superiors won't let him. When Liberman visits some of the homes of the men who are killed, he discovers that all of them have an adopted son who all resemble each other.