This hunky singer was studying sports medicine when he dropped out to join the vocal group 98 Degrees. His gamble paid off — even if the outfit wasn't the most successful of the wave of late-'90s boy bands. In 2002, Lachey considerably raised his profile by marrying pop princess Jessica Simpson. Together the couple launched the wildly popular reality series Newlyweds: Nick and Jessica in 2003, which featured Lachey suffering his bride's addle-brained antics. Although both their stars were on the rise with acting gigs and a handful of prime-time variety specials, the couple split in 2005.