Complex sentence: Some time before 1931, he adopted the name Liversidge from the married name of his eldest sister and in that year, applied for a Canadian passport in that name, claiming to have been born in Toronto and misstating his date of birth.
Split into simpler sentences: Some time before 1931 he adopted the name Liversidge (the married name of his eldest siste). In 1931 he applied for a Canadian passport in that name, claiming to have been born in Toronto and misstating his date of birth.