<human>: Give me the gist of the text in a nutshell

I am just recently engaged to a beautiful young woman and couldn't be any happier with our relationship. The problem we have stems not from ourselves, but from our divorced parents. 

A year or so prior to becoming engaged my father asked my then girlfriend and me if we cared if he dated girlfriend's mother. We were not comfortable with it and made our feelings about this known. Our dislike for the situation was played off as immature kids who will eventually come around, so they dated anyways. Fast forward a year and now I am happily engaged with girlfriend, and my father and her mother are in a serious relationship. My fiancé and I have never budged from our stance of being uncomfortable with our parents relationship, and it has caused extreme tension between our relationships with our parents. 

For just a little more background, my fiancé and I had been dating for over three years when our divorced parents decided to start seeing each other, and even at that time it was widely speculated that girlfriend and I would eventually marry. It's not as though both relationships happened around the same time. During those three years of dating we saw both our parents become divorced and then start seeing each other. This may add to our dislike of their relationship, along with what feels like a million other reasons. 

I could rant on and on about why my fiancé and I dislike their relationship, and if anyone would like more detail about the situation I am happy to give it, but what I really want opinions on is, "are fiancé and I wrong for making a big deal out of our parents being in a serious relationship?"  I just want to make sure our feelings of dislike, betrayal, and even disgust at the situation we have been put in are justified before more irreparable damage to our relationships with our parents is done. 

For further clarification, I love my fiancé and nothing our parents do will change that in any way. I would not have asked her to marry me if I felt like other people, even our parents could come between us. I'm strictly looking for relationship advice regarding us and our parents. Thanks.
<bot>: Dad is sleeping with future mother-in-law.  Fiancé and I aren't happy about it, and it is causing problems with our relationships with our parents.  Are our feelings justified?