These two names represent different people, but it must be noted that Peter van Daan is a pseudonym for Peter van Pels. After hearing a radio announcement in 1944 stating that documents such as diaries would be published after the war in order to preserve Jewish history, Anne wrote that she had always wanted to be a writer and composed alternate names for everyone hiding in the annex. Upon publishing Anne's diary after her death, Otto Frank elected to use the real names of his own family members but to maintain Anne's pseudonyms for everyone else.

Peter van Daan/van Pels and his family hid with Anne and her family in the secret area of Mr. Frank's office building; he died in Mauthausen concentration camp in 1945. Peter Wessel was a schoolboy Anne knew in the years before she and her family went into hiding; she remembered him while hidden in the annex and imagined a future romance with him. Anne knew Peter van Daan quite well (even too well) since they were sequestered together for so long, while her memories of Peter Wessel were shrouded in fantasy, used as a means of escape from grim reality.