Some relationships just aren't made to last. And 2006 proved it. Some celeb couples called it quits after more than a decade together (Bobby & Whitney), while others realized sooner that they were better off just being friends (Jen & Vince). From Reese & Ryan to Britney & K-Fed, here are the romances that went kaput in '06: 5. REESE & RYAN Just days after they announced their split -- after seven years of marriage and two kids (Ava, 7, and Deacon, 3) -- Phillippe told PEOPLE: "I'm not a perfect person, but I'm not guilty of a lot of the things I have been accused of." Still, the Flags of Our Fathers star brushed off reports that an alleged relationship with Australian actress Abbie Cornish was the catalyst for their demise. 4. WHITNEY & BOBBY As Whitney would say, "Hell to the no!" But the Grammy-winning singer decided it was "hell to the yes" when she filed for separation on Sept. 8 and a month later filed for divorce from her bad-boy husband Brown. The couple survived a reality show (Being Bobby Brown), rehab and run-ins with the law, but Houston finally decided it was her prerogative to end her 14-year marriage. 3. HEATHER & PAUL Things got really ugly after McCartney and Mills announced their separation in May, and he filed for divorce in July after four years of marriage. The land-mine activist claimed the ex-Beatle had been abusive to her. Tabloids posted topless photos from her younger days. Tired of sensational reports that she was after his estimated $1.8 billion fortune, Mills told TV's Extra in November, "Eighty-five percent of my income goes to my charity. The word gold-digger doesn't go with that." 2. JEN & VINCE Their first parting of the ways played out onscreen in The Break-Up. But Aniston and Vaughn conducted their 14-month-long relationship as far from the media glare as possible. During their courtship, they battled engagement rumors (Oprah's throwing them an $8 million wedding!) and talk that they'd split long before their reps' Dec. 5 announcement. In the end, they remained just "good friends." 1. BRITNEY & KEVIN Two years of marriage, two babies (Sean Preston, 1, and Jayden James, 3 months) and it was kaput for Spears and Federline when she filed for divorce on Nov. 7. Of course, the rumor mill had been predicting it all along. Now, Spears is reliving her single life on the town with new BFFs including Paris Hilton while Fed-Ex makes the rounds with his rap crew.