Kepler’s father-in-law scorned him for his humble finances

When Kepler met Barbara Müller, a 23-year-old widow (more than twice) with a small daughter named Regina Lorenz, he struck up a flirtatious relationship with her. Müller was the daughter of a prosperous manufacturing owner and the heir to the wealth of her late husbands. Her father Jobst initially opposed getting married. Despite having inherited his grandfather's nobility, Kepler was an unsuitable son-in-law because of his poverty.

He has a simple life and only makes enough money to provide for his kids. Jobst did not believe that Kepler's latest work, Mysterium, would bring him enough money to support his daughter and himself, let alone any children that might be born later. On April 27, 1597, Barbara and Johannes were united in marriage.

When Kepler embarks on a fundraising trip around Germany to support the release of his book, Johannes and Barbara's relationship is on the verge of disintegrating. Fortunately, a group of shared friends persuaded the young woman that having a distant vision does not imply having a distant heart. A fun fact from Johannes Kepler states that the pair wed in 1597 and had three kids. The Keplers had two children (Heinrich and Susanna) in the early years of their marriage, but both of them passed away in infancy. Susanna was born in 1602, and Friedrich was born in 1604.