Does having a "one who got away" in your life affect your current relationship?

I’m sure everyone here at least knows about or has experienced the idea of “the one who got away,” and by that I mean a person who you once had strong feelings for, and then for whatever reason, things ended or never came to fruition as you had hoped.

From my experience, there often seems to be nostalgia for that person, even if you are in a current relationship with someone that you love. Also, there sometimes seems to be a feeling of dislike towards that one person if things didn’t work out because “the one who got away” was the one who didn’t want it to work out.

I’ll give an example: My sister (twin) has a boyfriend currently. They have been together for about a year now and seem happy. However, before this current relationship, she was VERY interested in this guy named Andy. Things didn’t move past the “casual dating” stage because I don’t think Andy was as interested as my sister. Nowadays, whenever his name comes up, my sister says something like “he’s a douche bag” or “I’m not the biggest fan of his.” I get the feeling though that these bad feelings come from wishing they were together and blaming him for it.

So, my question is, does having ‘the one who got away’ in your life affect your current relationship in any way? Should it?