Simon Cowell and Lauren Silverman, 18 Years
This relationship is a little bit of a scandal. Lauren and Simon started dating while she was still with her husband, real estate mogul Andrew Silverman. After Lauren got pregnant with Simon's child in 2013, they had to go public.
Kevin Costner and Christine Baumgartner, 20 Years
Kevin, 65, and Christine, 45, have been married since 2004. They broke up before their marriage after Kevin said he didn't want any more kids since he already had four. Eventually, they reconciled and he changed his mind and they had three more together.