Quick question, what is it called when you are the last person someone dates before getting engaged?

You date someone, you break up, the next person they date becomes their fiance then husband. This starts happening in most of or all of your dating relationships. What is that called? I think that there was a movie about it in the early 2000s staring Dane Cook; but I might be misremembering the production details.
Quick question, what is it called when you are the last person someone dates before getting engaged?
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