Daniel Riggs, a former tennis coach in Fort Lauderdale, Florida, and the grandson of former professional tennis player Bobby Riggs, has been sentenced to 20 years in federal prison for engaging in a sexual relationship with two minor females that he coached. Daniel, 33, pleaded guilty to charges of coercing and enticing the women in question to engage in sexual activity, according to a press release from the Southern District of Florida. "Children and parents trust coaches with more than athletic instruction. They trust them with safety, guidance, and character," U.S. Attorney Jason A.