I've been working on my FIL's Tietjen line off and for the last three years. What we 'know'(right, LOL):
Claus(Charles) Tietjen born circa 1856 from Germany, parents unknown, interred March 9, 1890
married Meta(Martha, Mattie) Eichmann(not sure of the correct spelling) born 1854-1856, she was born in NY or Germany.
and they had the following children:
Martha Clara Tietjen born 1879, married twice according to 1900 census, only know of marriage to James S Cox in 1905, she dies 1913 of TB in Manhattan, no children
John Tietjen(not confirmed, but listed in family plot), born after 1880 census, interred age 6 in Dec 4, 1886
Louise Tietjen born circa 1883-1885, 'married' to John Henry Lavelle('son' of William A Lavelle), one son, James Ivan Lavelle, dies in 1912 of TB in Manhattan, she had lived with her sister Louise and BIL shortly before her death. In 1910, her son is living with the Cox family, but Louise is not listed with them.
Lily B Tietjen(not confirmed) born 1885, interred July 21, 1885
Margarette Tietjen(not confirmed) born circa Dec 1887/Jan 1888, interred June 27, 1888
Annie Tietjen(not confirmed) born circa Dec 1888/Jan 1889, interred July 12, 1889
Minnie Tietjen(not confirmed) born circa March 1890, interred October 19, 1890
After Claus's death in 1890, I find Martha Tietjen, widow to 'Chas' at the address where Minnie Tietjen died in 1890, on the 1894 Brooklyn Directory.
On the 1900 census in Brooklyn we find a possible match for Martha, married to a Hermann Langenhaupt, living with a possible match for her daughter Louise, and three other children Fred, Lily and Bertha. I went in search of 'Langenhop' as there were two Langenhop children who were buried in the Tietjen plot, Lillie and Bertha who were interred August 16, 1900.
I cannot find Herman or Fred Langenhop/Langenhaupt after 1900. I find a Meta Langenhop in what I assume is an institution in New Jersey on the 1920 census, and she is about the right age.
So, my next steps will be:
Find death certificates for the Tietjen/Langenhop children
Find where Martha/Meta is in 1910, and determine when she died.
Find Claus' death certificate in hopes of discovering his parents.