Karl Weierstrass was a German mathematician born in 1815 who never married or had children because he was focused on his work. He studied law but left without a degree to pursue mathematics, teaching secondary school for 15 years before joining the University of Berlin in 1856. Weierstrass made significant contributions to the theory of functions and is considered the father of modern analysis, though he suffered from poor health late in life, dying of influenza in 1897 at age 81.