Stuff like that happens all the time. A lot of time, you might still have some remaining feeling for each other or more feeling towards each other then your current partner. My friend Sam and her ex Emma for example, broke up due to a misunderstanding, because Sam thought Emma fall out of love with him and left. Emma ended up dating and married to another guy. When, they realized the misunderstanding Emma is already married. They still got feelings for each other, but it is too late, plus, despite the fact they still love each other, Emma's husband is also a nice guy and although Emma love Sam more, she also love her husband. The two of them decided never to meet again and go their seperate ways and now Sam is also married. But we all know, if both Emma and Sam's marriage failed, due to some form of reason and learn of each other's failed marriage, they would probably give their relationship another shot.