Princess Alexandra of Hanover, granddaughter of Grace Kelly, has announced her engagement to Ben Sylvester Strautmann. The couple have been together for a decade. Strautmann is a German former professional basketball player. Princess Alexandra displayed an 18-carat yellow and white gold diamond ring. The ring holds a diamond. Reports confirm the couple plans to marry. The engagement follows a decade-long romance. Grace Kelly's granddaughter and the former athlete are now preparing to marry after more than ten years together.