Johannes Kepler's birthplace. The German astronomer Johannes Kepler (1571-1630) was born on 27 December 1571, in the Free Imperial City of Weil der Stadt (near modern-day Stuttgart). His grandfather, Sebald Kepler, had been Lord Mayor, but by the time Johannes was born the family circumstances had changed, with Johannes' father being employed as a mercenary. Kepler devised the three fundamental laws of planetary motion. These laws were based on detailed observations of the planets made by himself and the Danish astronomer Tycho Brahe.