All of Johann Sebastian Bach’s surviving brothers were named Johann: Johann Rudolf, Johann Christoph, Johann Balthasar, Johannes Jonas, Johanna Juditha, and Johann Jacob. His father was Johann Ambrosius Bach.
By contrast, his sister, Marie Salome, “stuck out like a sore thumb,” writes Jeremy Siepmann in Bach: Life and Works. “And they all had grandparents and uncles and cousins whose names were also Johann, something. Johann Sebastian’s own children included Johann Gottfried, Johann Christoph, Johann August, Johann Christian, and Johanna Carolina.”
from Futility Closet https://www.futilitycloset.com/2018/01/12/theme-and-variations-2/