Peter was with Anne in Westerbork, and the two were often seen together. Once they got to Auschwitz, however, they were separated. When the Auschwitz prison guards fled the camp to avoid the oncoming Allies, they took most of the prisoners with them. Peter went with the group of prisoners led by the guards through the bitter winter weather. Many died along the way—of cold, hunger, or gunshot—and Peter was among them.
Sorry, but The Diary of Anne Frank states that Peter is taken with the SS as they try to escape from the Russian's, who are on the move. It states that Peter is never heard from again after that. I presume he is , sadly, dead by now. If you do not believe me go look in the "Afterword " of Anne's Diary.
He got ill and died while on a death march