Question: Who is the paternal grandfather of Johann Nicolaus Bach?

Knowledge 1: Johann Nicolaus Bach
Johann Nicolaus Bach (or Johann Nikolaus Bach) (– 4 November 1753) was a German composer of the Baroque period.Johann Nicolaus was the eldest son of Johann Christoph Bach and the second cousin of Johann Sebastian Bach.He was educated at the University of Jena, where he later became organist.He was probably born at Eisenach, where his father was employed as a musician, attended the Eisenach Latin school until 1689, and was a student of the Jena city organist J.M. Knüpfer, a son of Sebastian Knüpfer; after an Italian sojourn in 1696, he became organist at the Stadtkirche and the Kollegiatkirche in Jena.He was influenced by Antonio Lotti.He later joined the Danish army.He then returned to Jena where he lived for the rest of his life.Few of his compositions survive.He was also a maker of harpsichords and organs.Surviving pieces include a mass, two chorale preludes on  and a Singspiel "Der jenaische Wein- und Bierrufer", this in the form of a quodlibet on Jena student traditions. [SEP] Knowledge 2: Johann Christoph Bach
Johann Christoph Bach (baptised – 31 March 1703) was a German composer and organist of the Baroque period.He was born at Arnstadt, the son of Heinrich Bach, Johann Sebastian Bach's first cousin once removed and the first cousin of J.S. Bach's father, Johann Ambrosius Bach.He was also the uncle of Maria Barbara Bach, J. S. Bach's first wife and second cousin.Johann Christoph married Maria Elisabeth Wiedemann in 1667.They had seven children, including four sons who became musicians: Johann Nicolaus (10 October 1669 – 4 November 1753), Johann Christoph Jr. (29 August 1676 – 1738), Johann Friedrich (1682–1730), and Johann Michael (1685–unknown).Two of their grandsons later sailed to America and founded the Bach family there:Johann Heinrich Bach (1709–1789) and Johann Wilhelm Bach (1722–1794).He is not to be confused with Johann Sebastian Bach's son, Johann Christoph Friedrich Bach.Johann Christoph had a reputation as a composer that was only equalled by that of Johann Sebastian within the Bach family during his lifetime.He was organist at Eisenach and later a member of the court chamber orchestra there.His brother, Johann Michael Bach (Johann Sebastian Bach's father-in-law and Maria Barbara's father), was also a composer.Some of the works were later attributed to Johann Sebastian, but were recently recognized as written by Johann Christoph.One of the most famous works is the cantata , based on the "Song of Solomon".Despite his success as a musician, Johann Christoph experienced financial difficulties, which may have resulted in his not having been selected as the guardian of Johann Sebastian when the latter's parents died.Yet Johann Christoph found the money to have his portrait painted in oil several times, including the well-known portrait of him that is on display in a Berlin museum.Johann Christoph was heavily in debt when he died at Eisenach.He died just ten days after his wife Maria died.Sebastian Bach described him in his Genealogy (1735) as "the profound composer", thus hinting at his reputation, not just within the family, but within society.
Knowledge 1: Johann Nicolaus Bach
Johann Nicolaus Bach (or Johann Nikolaus Bach) (– 4 November 1753) was a German composer of the Baroque period.Johann Nicolaus was the eldest son of Johann Christoph Bach and the second cousin of Johann Sebastian Bach.He was educated at the University of Jena, where he later became organist.He was probably born at Eisenach, where his father was employed as a musician, attended the Eisenach Latin school until 1689, and was a student of the Jena city organist J.M. Knüpfer, a son of Sebastian Knüpfer; after an Italian sojourn in 1696, he became organist at the Stadtkirche and the Kollegiatkirche in Jena.He was influenced by Antonio Lotti.He later joined the Danish army.He then returned to Jena where he lived for the rest of his life.Few of his compositions survive.He was also a maker of harpsichords and organs.Surviving pieces include a mass, two chorale preludes on  and a Singspiel "Der jenaische Wein- und Bierrufer", this in the form of a quodlibet on Jena student traditions. [SEP] Knowledge 2: Johann Nicolaus Mempel
Johann Nicolaus Mempel( variants: Nikolaus, Mempell, Mämpel)( 10 December 1713 – 26 February 1747) was a German musician.
Knowledge 1: Johann Nicolaus Bach
Johann Nicolaus Bach (or Johann Nikolaus Bach) (– 4 November 1753) was a German composer of the Baroque period.Johann Nicolaus was the eldest son of Johann Christoph Bach and the second cousin of Johann Sebastian Bach.He was educated at the University of Jena, where he later became organist.He was probably born at Eisenach, where his father was employed as a musician, attended the Eisenach Latin school until 1689, and was a student of the Jena city organist J.M. Knüpfer, a son of Sebastian Knüpfer; after an Italian sojourn in 1696, he became organist at the Stadtkirche and the Kollegiatkirche in Jena.He was influenced by Antonio Lotti.He later joined the Danish army.He then returned to Jena where he lived for the rest of his life.Few of his compositions survive.He was also a maker of harpsichords and organs.Surviving pieces include a mass, two chorale preludes on  and a Singspiel "Der jenaische Wein- und Bierrufer", this in the form of a quodlibet on Jena student traditions. [SEP] Knowledge 2: Fujiwara no Nagara
, also known as Fujiwara no Nagayoshi, was a Japanese statesman, courtier and politician of the early Heian period.He was the grandfather of Emperor Yōzei.

Answer: Heinrich Bach