In 1971, Bill met Grace Cavert, of Jacksonville, at the Key Club youth state convention. That evening, Grace went home and woke her parents to tell them: "I've met the man I'm going to marry." Indeed, Bill and Grace were married a little more than a year later. And for 33 years now, they have been a devoted, loving couple. Since returning from their honeymoon, when they went door to door together to campaign for Bill's first race for the Florida Legislature, they have been a team. Grace has been involved in, and incredibly supportive of, Bill's public service, while also pursuing her own interests, which include humanitarian aid for developing regions of the world and helping the underserved in our own communities. During Bill's years in Congress, Grace was President of the International Club, which promotes friendship and understanding among women worldwide.

Bill and Grace have two grown children, Bill Nelson, Jr., and Nan Ellen Nelson. Being their father has always been important to Bill, because he lost his own father at an early age. He understands the importance of parents spending time with their children.