Samuel KOESTLER  ca 1815 -? | his parents
& Teresa "Resie" STEINHARDT  | her parents
of Bohemia

This is my working hypothesis - the way I see it as of this moment!! 

Samuel Koestler married Teresa "Resie" Steinhardt in Bohemia.

Children of Samuel Koestler and Teresa "Resie" Steinhardt:
1. Lena Koestler 22 Dec 1843 Bohemia - 24 Apr 1910 NYC
             resident of US 16 years at death (arrived 1894)
      married Marcus Koestler [her 1st cousin]
     a. Adolph Koestler 17 Jan 1870 - 19 Nov 1923 NYC
               dry goods merchant  arrived US 16 May 1885 naturalized 26 Aug 1892
            married 1902 Malvina Beck 1880 - 19 Oct 1960 NYC
             i. Monroe Koestler 1902 - 1968 NYC
            ii. Albion Koestler 1907 - 1971 NYC
                  (a) Anthony Koestler  
           iii. Leona R Koestler 1913 - ca 1970 NJ
     b. Rosie Koestler ca 1874 -                                she emig in 1899
           married ca 1898 Mayer (Maier) Tilbor ca 1872 -    he emig. in 1894
                    Produce Dealer Market     In 1910 Richmond, Richmond NY
              i. Dora Tilbor 1899 -                                  she emig. in 1899
    c. Carl Koestler  15 Jan 1878 - 29 July 1927 NYC
            dry goods merchant  arrived US Aug 23 1893 naturalized 26 July 1901
          married Evelyn Hoffman 1881 -1953 NYC
              i. Milton Koestler 1913 - 1969 NYC
2. Morris (Moritz) Koestler 27 Jan 1849 Bohemia - 23 Jan 1936 Elizabeth, NJ
                 resident of US since 1868  naturalized 28 Oct 1878
        married Jennie Krauskopf 1845 -1921
3. Mary Koestler
        married Sigmund Kouper

Melvin Koestler in his letter to Anthony Koestler dated 31 May 1977:
"You may be interested in looking in Who's Who of American Women (first edition 1958) where you will find the names of Elsa Koestler and Mrs. Albion Koestler and Frances (Mrs. Milton) Koestler."