Joseph Stalin did not trade German prisoners for his own son.

Soviet dictator Joseph Stalin really did hate his son Yakov. In fact,
Stalin refused to surrender German soldiers in exchange for releasing his
son from capture during World War II. In 1943, Yakov Stalin reportedly
committed suicide while being held prisoner in a German concentration camp.
Stalin is thought to have despised his first born son, which may be due to
his beloved first wife dying when Yakov was just nine months old. At the
funeral, he claimed that his wife had softened his hard heart and without
her he would never be able to love anyone again. Although Stalin remarried
and had another son and a daughter, his relationship with his oldest son
was so contentious that Yakov attempted suicide as a result, leading the
dictator to scoff about his son’s poor gun aim.