Romantic interest after marriage?

[Janna]

I am doing a Random Town Jump; had my sim meet up with the male I wanted her to, Kearney O'Shea.  Had her asked if he had any RI, says no.  A couple of days later she invites him to her home.  He immediately starts a romance with her, surprised as he isn't flirty and she is.

Invites him to stay over night and he does, romancing the next day and by evening they were married.  I checked his relationship to see who he was friends with and there was this person, wasn't sure if male or female from name and looks.  Just noted as friend.

Looked today while I was playing and she (or he?) is noted as romantic interest.  This has me confused, he is constantly romancing his wife, starting the romance  by flirting, stroke cheek, kiss without my having to tell him.  No problem in getting the woohoo to come up. 
With what I have going on, he doesn't have time to do anything but go to work and come home. 
So, why does he have this romantic interest, how does it affect the game?  She doesn't seem to know that he has one, although I don't have her out a lot, family is taking up time. 
So far I can't find the person he has the RI with, looked in edit town and can't find her, am going to do a better search next time I play.

Mainly confused and curious how this could happen and what it will do to my sims couple relationship. 

[Jamie]

You can click her picture in the relationship panel to invite her over then ask her to just be friends. She could be an NPC. That's really weird. It's never happened to me as far as I can remember.

[azokka361]

The "Ask to Be Single" only shows if they have a boyfriend/girlfriend or higher, not romantic interests. Sims with romantic interests will flirt with other sims and respond to other sims' flirting. If your sim finds out about it she will not be happy, and will either autonomously fight or break up with him, so you want to find her and break them up fast.

[Janna]

I guess what has me confused was that his RI wasn't there when they married.  I had checked his relationships as soon as they married.  She changed from friend to RI around a week after they married.
Once I had a created sim marry a townie and saw that he had a romantic interest and I didn't do anything about it and twice he cheated on his wife so I kicked him out.

Wanted to make sure this one didn't have one and it didn't show up for several days. 
Could this be one of the quirks of the relationship problems?  After the sim cheated on his wife (my created sim), I decided to create married couples when I play a new town, so it has been a long, long time since I have created a single sim who marries a townie. 

I'm going to hunt her down and break up the relationship, can't  have it messing up my project, just surprised it showed up after they had been married for several days.  Neither one has commitment issues, and she has the flirty trait, not him. 

[Turoskel]

Is he inappropriate? if so he could have kissed this woman when you weren't watching him perhaps. They'll kiss anybody if they feel like it, married or not.

[Janna]

Kearney O'Shea (as does his twin) has the traits of Brave, Handy, Athletic, Charismatic and Ambitious.  He has the LTW as Astronaut and his brother Breandan has the LTW of Super Spy (I think).
Three times that I have played that town Breandan has been a vampire and Kearney has been human, or rather an elven. 

I'm wondering if the Charismatic could be a factor, hadn't thought about that until I listed his traits. 

I am going to have to hunt her up and break them up, don't need this romance breaking up before they can move on to the next town in the project.

I could understand it being there if she had been his RI before marriage to Brittney, but to show up after a week or more of marriage?  That is what has me a bit confused.