1. Justin Timberlake & Britney Spears Years Together: Dated from 1998 to 2002. Why They Split: The all-telling pop jams tell us that JT thought Britney was unfaithful. Why They're Better Off Together: Though their careers (and, namely, public images) have taken very disparate paths, these two seemed to make each other wickedly happy. Plus, we hope a reunion would happen by way of Britney vs. Justin nightclub dance floor showdown.