Pieter Schaap was the son of Lion Schaap and Jitha Krant. He married Schoontje van Kollem in Hilversum in 1939. She was the daughter of Aäron van Kollem and Naatje van Dijk. The couple had one daughter, Jitha.
In may 1943 the family moved to Amsterdam, Retiefstraat 2-I.
Amsterdam Municipal Archives; record card of Pieter Schaap