Paul Burck

Paul Burck was a nephew to my grandpa, Albert Gburek. At least letters between the two referred to each other as nephew and uncle. The exact connection is what I am searching for. Paul lived in Pittsburg, California and grandpa in Chicago. I found Paul on the 1930 census and on a WW2 draft registration card, which has the same address as his letters to grandpa. The 1930 census has him at 236 East 6th St., Pittsburg, CA with the following people:
George Mangues age 39, head, married age 34, born Ohio, parents born Ohio
Kathryn Mangues age 32, wife, married age 25, born Hungary, parents born Hungary, immigrated 1909
Margurite Baer age 15, stepdaughter, born Canada Calgary, parents born Hungary
Anna Baer age 8, stepdaughter, born Montana, parents born Hungary
Paul Burck age 43, stepfather, married age 24, born Germany, parents born Germany, immigrated 1923
Anna Burck age 52, mother, married age 33, born Hungary, parents born Hungary, immigrated 1923
I'm gathering Anna was married prior and Kathryn is her daughter and that Kathryn was also married before to a Baer because of the children's surname.
On the WW2 card, it has Paul’s date of birth as 27 April 1886 and says he was born in Waldau, Germany. It also asks who will always know you and that is filled in saying Mrs. Ralph Washburn, Box 147, Clear Lake, Highlands, Calif.
Then on the California death index I find an Anna Burck born 23 Nov 1877 and died 3 Oct 1958. Fathers last name Heimann and mothers maiden name Bavele. So I look for Kathryn with mother's maiden name Heimann and I find a Kathryn Washburn born 9 Mar 1899 whose fathers surname was Papp and her death date is 13 Apr 1983. I also find a Margaret Baer born 23 Nov 1914 who died 9 May 1969 and her mother's maiden name was Papp. I do not know if these are the same people or not but the clues are looking good.
Grandpa was the youngest of 14 children and he was born 27 Feb 1883 in Waldowo, Poland. Waldowo was Waldau back at the time of their births when it was Prussia. Grandpa’s baptism was found in the Topolno parish but I did not find a birth for Paul there. I then found a 1900 Mecklenburg-Schwerin census for a Theophiel Gburek whose date of birth is 27 Apr 1886, which is the same as Paul’s date of birth, and the place of birth is Waldau, Schwetz, Posen. I'm not good on transcriptions but it looks like he is a stepson to the head of house who is Johann Murawski born 24 Jan 1865 in Taschauerfelde, Schwetz; then Johann's wife is Margarethe Murawski born 7 Mar 1867 in Budin, Schwetz; other children are Pelagia Murawski born 11 Jul 1891 in Schwetz, Marie Murawski born 20 May 1893 in Schwetz, Antoni Murawski born 1 May 1898 in Prenzlau, and then I think the next person is just a boarder, Albert Rutkowski born 18 Jun 1855.
Grandpa’s parents married in Drzycim parish and the first 9 children’s births are found there including a Margaretha born 7 Mar 1867 in the town of Rowienica. Is this the same Margarethe on the 1900 census? The census says she was born in Budin and there is a Budyn south of Drzycim and the birth date does match. More research needs to be done in the surrounding parishes down around Waldowo to find Paul's birth but my gut is telling me I'm getting close to solving this puzzle.