Do you know when Henry Sander died? If not, I see from the birth certificate of his son, Richard, that Henry Sander was a tailor.
In the Manhattan City directories:
1889; Sander Henry, tailor, h. 94 First av,
1890; Sander Henry, tailor, h. 42 Av D
1891; Sander, H'y, tailor, h. 42 Av D.
Henry Sander the tailor is not listed after that, there IS a "Sander Mary, wid. of H'y" in the directories at various addresses starting in 1892.
In the NY City death index there is:
Heinrich Sander, 48 y, died Oct 9 1890, cert # 35316, Manhattan
His age of 48 years gives him a birth year of about 1842 which matches exactly with the birth year that can be calculated from his age of 39 years given on his son's 1881 birth cert. The death date of Oct 1890 may have been late enough in the year for him to be included in the 1891 city directory.
It might be worth your while to send for that death certificate.