Identified with family number 25 in many records of his children from both marriages.Brewery owner Hermann (from Jacob's marriage to Caroline) reported the death of "his brother" Mendel, naming Mendel's mother as Rosel.

The birth records for Nanny (1), Jacob and Handel name only their father; however, there is no reason to doubt that Rosel geb, Feldmann was the mother of all of Jacob's children up to her death in 1831.

Jacob appears to have had two daughters, both named Nany or Nanny, who were alive at the same time:

• Nanny (1) married in 1829, her father is Jacob Mueller, Arrendator in Rybnik, family number 25. From this she could not have been born later than 1813.
• In 1824 a Nany was born to Jacob Mueller and Rosel geb. Feldmann, family number 25. In 1826 Nanny, daughter of Arrendator Jacob Mueller, family number 25, died aged 2.25 years and was buried in Rybnik; this must be Nany born in 1824.

Thus Nanny (1) was alive throughout Nanny (2)'s short life.

Jacob is described as

• a Haendler or Haendelsmann (merchant) at Moritz's and Dorel's births (1813 and 1815),
• a Brandweinbrenner (brandy distiller) at Mendel's and Jettel's births (1817 and 1827),
• an Arrendator or Gastwirt (inkeeper) at Louis's birth (1825), Nanny (2)'s death (1826), Nanny (1)'s marriage (1829) and at the birth of his children from 1835 to 1841, and
• a Brauerei besitzer (brewery owner) at Louis's marriage (1849) and at his death (1856), as well as at Klara marriage (1859) and Mendel's death (1891).

Died aged 74 years on 30.04.1856 so born 1781-82.