:::::::::The book (Stefan Kornelius, Angela Merkel: Die Kanzlerin und ihre Welt, Hoffmann und Campe, 2013, page 1915, ISBN-13: 978-3455502916), all the articles are based on, literally states that he was a "German citizen" with "Polish roots" → . ⇒ Not once, in the whole book, the term "Pole" is used! ⇐  

 :::::::::The Guardian newspaper has properly cited the passages in question: 

 :::::::::⇒ "Not only was her grandfather of Polish origin, the chancellor almost was born Angela Kazmierczak. Her grandfather was a Ludwig Kazmierczak, born 1896 in Poznan – then part of the German Reich. The family was proud of its Polish roots. Obviously not grandpa Ludwig who emigrated to Berlin when Poznan became Polish again after the first world war. He married a Berlin woman, and they had a son – Horst Kazmierczak, Angela's father. The family decided to cut their Polish roots in the early 30s. The Kazmierczaks followed a common fashion and Germanised their family name to Kasner."  ⇐ 

 :::::::::Per WP:RS, the original secondary source, i.e. the book, does supersede the newspaper articles that are merely based/cite from that source! I demand, per several WP policies, that this book is used as the main reference!