1. MD 1860 Census, Baltimore City, 17th Ward, p. 246 (9 July 1860)
Marker, Mathias 30 Ocupation:Tailor Born: Germany
Elizabeth 20 Born: Germany
Catherine 2 Born: Maryland
Elizabeth 6/12 Born: Maryland
Note: This is pretty much the information you found, but you had Mathias' age as 20 and Elizabeth's (wife)
birthplace as Maryland.

2. PA 1870 Census, Allegheny Co., Pittsburgh, 13th Ward, p. 496 (19 August 1870)
Markus, Mathias 42 Occupation: Tailor Born: Germany
Cecelia 31 Born: Germany
Cath 13 Born: PA ?
Henrietta 3 Born: PA
Henry 1 Born: PA
Note: There is a different surname "Markus" and the wife's given name is listed as "Cecelia," but the fathers first name, occupation, birth place of parents, and Catherine's name and ages between the 1860 and 1870 in the words of the researcher "leave no doubt that the family listed in the 1870 census is the same family."

3. PA 1880 Census, Allegheny Co., Pittsburgh, 11th Ward, 2nd Precinct, Enumeration District 121, sheet 15, line 19 (4 June 1880)

Marker, Mathias 50 Occupation: Saloon Keeper Born: Self-Prussia; Father & Mother-Germany
Lizzie 41 Born: Same as Mathias
Annie 13 Born: PA
Henry 10 Born: PA
Hattie 8 Born: PA
Lizzie 6 Born: PA
Emma 4 Born: PA
Martha 1 Born: PA
Note: By June 1880 Catherine had moved out of her parents home. The date I have for Catherina and John
[Johannes] Abplanalp's marriage is April 11, 1880, so that is consistent with this census data. I will ask this same researcher to look for John and Catherine in the 1880 Census. Herrietta, age 3 in 1870, is listed as "Annie," age 13 in 1880.

4. Church Records: The marriage [in America, the birth date of Catherina in December suggests a possibility that they may have been married earlier in Germany] of Mathias Marker and Elizabeth Grabin, 11 September 1857, baptism [4 April 1858] for Cathar. Wilhelmina Marker [born 17 December 1857], and baptism [5 July 1860] for Catharina Elis. [born 4 February 1860] are recorded in German in the register of St. Stephens Evangelical Lutheran Church, Hanover and Hancock Streets, Baltimore. The church marriage record indicates that both Mathias Marker and Elizabeth Grabin were born in Waldeck, at the time an independent province in central Germany [now the state of Hessen].

5. Passenger Lists: Mathias Marker and Elizabeth Grabin left Brennen on the ship Julius and arrived in
Baltimore 10 August 1857. They were passenger numbers 172 and 174 with ages listed as 27 and 18. The
passenger listed between them is Cathr. Grabin, age 20, in all likelihood Elizabeth's older sister.

If you or anyone on the Marker listserve can add to or use this information, i.e. you are related to Catherina's siblings, please go ahead with it and/or communicate withg me, Richard Hulme