Kevin Costner and Christine Baumgartner — 20 years
Kevin Costner and Christine Baumgartner have been together as a married couple since the year 2004. However, prior to their nuptials, they had a brief separation, which was caused by Costner’s initial reluctance to have more children, as he already had 4 from his previous relationships. But, after some time, he had a change of heart, and they went on to have 3 more kids together, making him a father of 7 in total.
It's not like the women are teens... Most are at least 30.